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  • 1. Table Of Contents 1. PURPOSE AND SCOPE OF THE DOCUMENT....................................1 1.1. USERS OF THE DOCUMENT.........................................................................1 1.2. ASSOCIATED DOCUMENTS..........................................................................1 2. INTRODUCTION......................................................................................2 2.1. DATABASE MANAGEMENT SYSTEMS (DBMS)..............................................3 2.2. TYPES OF DBMS...................................................................................4 2.2.1. Relational DBMS............................................................................4 2.2.2. HIERARCHICAL DBMS................................................................6 2.2.3. Net Work DBMS.............................................................................7 2.3. SAMPLE DB2 DATABASE...........................................................................8 3. STRUCTURE OF DB2...............................................................................9 3.1. HIERARCHY OF DATA STRUCTURES.............................................................9 3.2. DATABASES.............................................................................................9 3.3. DB2 STORAGE GROUPS............................................................................9 3.4. TABLE SPACES.........................................................................................9 3.4.1. Simple Tablespace..........................................................................9 3.4.2. Segmented Table Space..................................................................9 3.4.3. Partitioned Table Space.................................................................9 3.5. TABLES..................................................................................................9 3.6. INDEX SPACES.........................................................................................9 3.7. INDEXES.................................................................................................9 3.8. VIEWS...................................................................................................9 3.9. SYNONYMS.............................................................................................9 3.10. ALIASES...............................................................................................9 3.11. DB2 CATALOG......................................................................................9 3.12. DB2 DIRECTORY...................................................................................9 3.13. ACTIVE AND ARCHIVE LOGS....................................................................9 3.14. BUFFER POOLS......................................................................................9 4. DATA TYPES............................................................................................39 4.1. NUMERIC DATA.....................................................................................39 4.1.1. Nulls.............................................................................................39 4.2. STRING DATA........................................................................................39 4.3. CHARACTER FORMAT..............................................................................39 4.4. DATE/TIME DATA..................................................................................39 4.5. EQUIVALENT COBOL DECLARATIONS OF DATA TYPES...................................39 5. SQL PROGRAMMING...........................................................................49 5.1. DDL STATEMENTS.................................................................................51 5.1.1. Create Database...........................................................................51 5.1.2. Create Table Space.......................................................................51 ©Case Consult (India) Pvt. Ptd. 03/1998 i DB2 Fundamentals /home/pptfactory/temp/20100719111436/db2-referencedoc1182.doc
  • 2. 5.1.3. Create Table.................................................................................51 5.1.4. Create View..................................................................................51 5.1.5. Create Index.................................................................................51 5.1.6. Alter Table....................................................................................51 5.1.7. Drop..............................................................................................51 5.2. DML STATEMENTS................................................................................64 5.2.1. Select............................................................................................64 5.2.2. Joining Tables...............................................................................64 5.2.3. Sub Queries..................................................................................64 5.2.4. Union............................................................................................64 5.2.5. Insert.............................................................................................64 5.2.6. Update..........................................................................................64 5.2.7. Delete...........................................................................................64 5.3. CONTROL STATEMENTS............................................................................82 5.3.1. Grant............................................................................................82 5.3.2. Revoke..........................................................................................82 5.3.3. Commit.........................................................................................82 5.3.4. Roll Back......................................................................................82 6. PROGRAM STRUCTURE......................................................................87 6.1. HOST VARIABLES...................................................................................87 6.1.1. Declaring Host Variables.............................................................87 6.2. INDICATOR VARIABLES............................................................................87 6.3. SQLCA..............................................................................................87 6.4. COBOL STRUCTURE OF SQLCA..............................................................87 6.5. SQLCA RETURN CODES........................................................................87 6.6. SQLCA WARNINGS..............................................................................87 6.7. IMPORTANT SQL CODES..........................................................................87 6.8. STATIC SQL.........................................................................................87 6.9. DYNAMIC SQL.....................................................................................87 6.10. EXAMPLE FOR A DB2 APPLICATION PROGRAM.........................................87 7. PROGRAM PREPARATION ...............................................................122 7.1. STEPS IN PROGRAM PREPARATION............................................................122 7.2. DCLGEN (DECLARATIONS GENERATOR )..................................................122 7.3. PRECOMPILE........................................................................................122 7.4. BIND.................................................................................................122 7.4.1. Binding A DBRM To A Package.................................................122 7.4.2. Binding An Application Plan......................................................122 7.5. COMPILE AND LINKEDIT........................................................................122 7.6. OVERVIEW OF DB2 APPLICATION PROGRAM PREPARATION AND EXECUTION...122 7.7. ASSOCIATING LOAD MODULES AND PACKAGES..........................................122 8. SECURITY FEATURES........................................................................140 8.1. PRIVILEGES.........................................................................................140 8.2. REFERENTIAL INTEGRITY........................................................................140 8.2.1. DB2 Enforcement Of Referential Integrity.................................140 ©Case Consult (India) Pvt. Ptd. 03/1998 ii DB2 Fundamentals /home/pptfactory/temp/20100719111436/db2-referencedoc1182.doc
  • 3. 8.2.2. Referential Integrity Enforcement Rules....................................140 8.2.3. Example For Referential Integrity Violation..............................140 8.3. DATABASE RECOVERY IN CASE OF FAILURE.............................................140 8.3.1. Unit Of Recovery........................................................................140 8.3.2. Data Recovery............................................................................140 9. CONCURRENCY...................................................................................157 9.1. CONCURRENCY....................................................................................157 9.2. LOCKING STRATEGY..............................................................................157 9.3. LOCK SIZES AND TYPES........................................................................157 9.4. ACQUIRE RELEASE PARAMETERS.............................................................157 9.5. ISOLATION PARAMETER..........................................................................157 10. DB2I (DB2 INTERACTIVE )..............................................................167 10.1. DB2I..............................................................................................167 10.2. SPUFI............................................................................................167 11. UTILITIES............................................................................................171 11.1. LOAD...............................................................................................171 11.2. RUNSTATS.........................................................................................171 11.3. REORG.............................................................................................171 12. ADVANCED DB2..................................................................................179 12.1. MORE ABOUT INDEXES.......................................................................179 12.1.1. Example Of An Index................................................................179 12.1.2. Clustered Indexes.....................................................................179 12.1.3. Non Clustered Indexes..............................................................179 12.2. SPECIAL REGISTERS............................................................................179 12.3. MORE ABOUT LOCKS.........................................................................179 12.3.1. Modes Of Table And Tablespace Locks....................................179 12.3.2. Modes Of Row And Page Locking............................................179 12.3.3. Lock Mode Compatibility Of Table And Table Space Locks....179 12.3.4. Lockmode Compatibility Of Row And Page Locks...................179 12.4. INVOKING ONLINE UTILITIES................................................................179 ©Case Consult (India) Pvt. Ptd. 03/1998 iii DB2 Fundamentals /home/pptfactory/temp/20100719111436/db2-referencedoc1182.doc
  • 4. 1. Purpose and Scope of the Document The Purpose of this document is to train fresh Software Engineers who would like to get familiarised with DB2 and as a reference material for application programmers. 1.1. Users of the Document This document is intended for database designers, database application programmers, students and teachers and more generally anyone who wishes to broaden his or her knowledge of the database, DB2. 1.2. Associated Documents No associated documents
  • 5. 2. Introduction DB2 ( IBM DATABASE2 ) is a highly successful relational database management system. DB2 enables it’s users to create, update and control relational database using STRUCTURED QUERY LANGUAGE (SQL). Designed to meet the needs of small and large business alike, DB2 is available on a number of platforms. we will be dealing with DB2 on MVS. RISC SYSTEM/6000 DB2 FOR DB2 FOR OS/2 AIX DB2 FOR DB2 FOR DB2 FOR HP-UX SOLARIS WINDOWS /NT DB2 FOR SINIX DB2 FOR MVS DB2 FOR OS/400 DB2 FOR VSE & VM
  • 6. 2.1. Database Management Systems (DBMS) DATABASE MANAGEMENT SYSTEMS deal with the problem of storing and retrieving large amounts of data. DBMS provides an environment to share data among it’s users. Preserving the correctness of data and restoring the database in failure are major concerns for DBMS. DBMS DATABASE APPLICATION PROGRAM QUERY PROCESSOR STORAGE MANAGER DATA ♦ DBMS CONSIST OF DATA, HARDWARE, SOFTWARE AND USERS ♦ BENEFITS OF DBMS ARE • REDUCE REDUNDANCY • AVOID INCONSISTENCY • SHARE DATA • MANIPULATES DATA EFFICIENTLY • FAULT TOLERANT • DATA INDEPENDENCE
  • 7. 2.2. Types Of DBMS Depending on data models used, database management systems are mainly divided into three. ♦ RELATIONAL DBMS ♦ HIERARCHICAL DBMS ♦ NETWORK DBMS 2.2.1. Relational DBMS DB2 is based on relational data model which was formulated by DR. E.F CODD in 1970. Relational systems have their origin in the mathematical theory of relations. Using relational data model , IBM developed DB2 in 1983. A RELATIONAL SYSTEM IS A SYSTEM IN WHICH ♦ THE DATA IS PERCEIVED BY THE USER AS TABLES ♦ QUERIES ARE USED TO EXTRACT DATA FROM THE DATABASE. ♦ ALL DATA VALUES ARE ATOMIC. ie EVERY ROW AND COLUMN POSITION CONTAINS ONLY ONE DATA VALUE; NEVER A LIST OF VALUES ♦ EXAMPLE OF RELATIONAL DBMS IS DB2 SAMPLE DATABASE FOR COMPARING DIFFERENT DBMS TABLE S TABLE SP S# SNAME STATUS CITY S# P# QTY S1 SMITH 20 LONDON S1 P1 300 S2 JONES 10 PARIS S1 P2 200 S3 BLAKE 30 PARIS S1 P3 400 S2 P1 300 S2 P2 400 TABLE P S3 P2 200 P# PNAME COLOR WEIGHT CITY P1 NUT RED 12 LONDON P2 BOLT GREEN 17 PARIS P3 SCREW BLUE 17 ROME P4 SCREW RED 14 LONDON
  • 8. ♦ TABLE S represents SUPPLIERS. Each supplier has a unique SUPPLIER NUMBER (S#), a SUPPLIER NAME (SNAME), a RATING (STATUS) and a LOCATION OF THE SUPPLIER (CITY). ♦ TABLE P represents PARTS. Each kind of part has a unique PART NUMBER (P#), a PART NAME (PNAME), a COLOUR (COLOR), a WEIGHT (WEIGHT) and a location where the PART IS STORED (CITY). ♦ TABLE SP represents SHIPMENTS. It connects other two tables. It REPRESENTS a shipment of parts of kind P1 by the supplier called S1 and the shipment quantity. ♦ In a relational data model TABLES are called RELATIONS, ROWS are called TUPLES and COLUMNS are referred as ATTRIBUTES. ♦ In a relational data mode association of ROWS of different TABLES are done using COLUMN VALUES of common columns. ♦ DB2 relates TABLE S and SP using the COLUMN SUPPLIER NUMBER(S#). TABLE P and SP are related using the COMMON attribute PART NUMBER (P#). TABLES S and P are related using COLUMN (CITY)
  • 9. 2.2.2. HIERARCHICAL DBMS Hierarchical View Of Supplier And Parts Database In hierarchical database suppliers, parts and shipments are different databases SUPPLIERS DATABASE PARTS DATABASE S1 P1 S2 ….. SMITH NUT JONES 20 RED 12 LONDON 10 LONDON SHIPMENTS DATABASE PARIS SHIPMENT SEGMENT LCHILD ♦ In this view data is represented by a simple TREE STRUCTURES and DBMS links these data bases using pointers. ♦ The user sees three individual trees for supplier database, each tree has a parent supplier. Each tree can be called a supplier record occurrence. Similarly you can see part record occurrence and shipment record occurrence. ♦ Shipment database contains the shipment quantity. The logical child of shipment database consists of supplier number , part number and pointers to corresponding databases .Similarly the supplier and parts databases also contains logical child which points to the shipment database. Now the user can access shipment from supplier and part databases. Similarly parts and supplier databases are also accessed from shipment database ♦ IMS (Information management system) is an example of Hierarchical DBMS
  • 10. 2.2.3. Net Work DBMS SUPPLIER PART RECORD RECORD SET SET S1 SMITH….. P1 NUT ….. S2 JONES….. P2 BOLT……. QUANTITY RECORDS 300 400 ……. ♦ NETWORK DBMS consists of owner databases and member databases. The member database can be accessed only via the owner database. ♦ In the example there are two owners for a member database. Supplier and part record sets are owners of shipment record set. Using this database the user can access the shipment of a particular part by a specific supplier ♦ The supplier S1 supplies part P1 of quantity 300. From the supplier S1 there is a pointer towards the supplied quantity and another pointer connects this to the corresponding part. An owner can have more than one pointer towards different quantities. ♦ Example of network database is IDMS(Integrated database management system)
  • 11. 2.3. Sample Db2 Database The sample database consists of THREE tables and these tables are used through out this book. TABLE S TABLE SP S# SNAME STATUS CITY S# P# QTY S1 SMITH 20 LONDON S1 P1 300 S2 JONES 10 PARIS S1 P2 200 S3 BLAKE 30 PARIS S1 P3 400 S4 CLARK 20 LONDON S1 P4 200 S5 ADAMS 30 ATHENS S1 P5 100 S1 P6 100 S2 P1 300 TABLE P S2 P2 400 S3 P2 200 P# PNAME COLOR WEIGHT CITY S4 P2 200 S4 P4 300 P1 NUT RED 12 LONDON S4 P5 400 P2 BOLT GREEN 17 PARIS P3 SCREW BLUE 17 ROME P4 SCREW RED 14 LONDON P5 CAM BLUE 12 PARIS P6 COG RED 19 LONDON ♦ TABLE S represents SUPPLIERS. Each SUPPLIER has a unique SUPPLIER NUMBER (S#), a SUPPLIER NAME (SNAME), a RATING (STATUS) and a location of the SUPPLIER (CITY). PRIMARY KEY IS S#. ♦ TABLE P represents PARTS. Each kind of part has a unique PART NUMBER (P#), a PART NAME (PNAME), a COLOUR (COLOR), a WEIGHT (WEIGHT) and a LOCATION where the PART IS STORED (CITY). PRIMARY KEY IS P# ♦ TABLE SP represents SHIPMENTS .It connects other TWO TABLES .It represents a SHIPMENT of PARTS OF KIND P1 by the SUPPLIER called S1 and the SHIPMENT QUANTITY. For a given SHIPMENT the combination of S# and P# is unique .That is the PRIMARY KEY is the COMBINATION of the above mentioned and the FOREIGN KEYS ARE S# AND P#
  • 12. 3. Structure Of DB2 This chapter deals with the definitions and examples of objects present in DB2.The topics included in this chapter are 3.1. Hierarchy Of Data Structures 3.2. Databases 3.3. DB2 Storage Groups 3.4. Table Spaces 3.4.1. Simple Tablespace 3.4.2. Segmented Table Space 3.4.3. Partitioned Table Space 3.5. Tables 3.6. Index Spaces 3.7. Indexes 3.8. Views 3.9. Synonyms 3.10. Aliases 3.11. DB2 Catalog 3.12. DB2 Directory 3.13. Active And Archive Logs 3.14. Buffer Pools
  • 13. STRUCTURE OF DB2 THE ELEMENTS OF DB2 ARE DIVIDED INTO TWO BROAD CATEGORIES DATA STRUCTURES SYSTEM STRUCTURES ♦ DATA STRUCTURES CONTAIN USER DATA AND ARE ACCESSED UNDER USER’S DIRECTION. ♦ SYSTEM STRUCTURES ARE CONTROLLED AND ACCESSED BY DB2 ♦ DATA STRUCTURES CONSIST OF • DATABASES • DB2 STORAGE GROUPS • TABLE SPACES • TABLES • INDEX SPACES • INDEXES • VIEWS • SYNONYMS • ALIASES ♦ SYSTEM STRUCTURES MAINLY CONSIST OF • DB2 CATALOG • DB2 DIRECTORY • ACTIVE AND ARCHIVE LOGS • BUFFER POOLS
  • 14. HIERARCHY OF DATA STRUCTURES DATABASE D1 STORAGE GROUP G1 TABLE SPACE S1 TABLE T1 TABLE T2 VOLUME 1 (DASD) INDEX X1 VOLUME 2 (DASD) INDEX X2 TABLE T3 PARTITIONED PART 1 TABLESPACE S2 TABLE T3 STORAGE PART 2 GROUP G2 VOLUME2 (3380) PARTITIONED INDEX X3 PART 1 PARTITIONED INDEX X3 PART 2
  • 15. Hierarchy Of Data structures ♦ The total collection of stored data is divided into a number of disjoint databases. They are USER DATABASES and SYSTEM DATABASES. ♦ Each database is divided into a number of disjoint ‘spaces’, that is several TABLESPACES and INDEX SPACES. A space is a dynamically extendible collection of PAGES, where PAGE is a block of physical storage. ♦ Each table space contains one or more stored tables. A stored table contains a set of stored records. A given stored table must be wholly contained within a single table space. ♦ Each INDEXSPACE contains exactly one index. A given index must be wholly contained with in a single index space. A given stored table and all of its associated indexes must be wholly contained within a single DATABASE. ♦ Each space (TABLE SPACE or INDEX SPACE) has an associated STORAGE GROUP. When a space needs to be extended, storage is acquired from appropriate storage group.
  • 16. DATA BASES DATABASE1 TABLESPACE1 INDEX 1 TABLE 1 TABLE 2 INDEX 2 TABLESPACE 2 ♦ DATABASE IS A COLLECTION OF A NUMBER OF TABLE SPACES ALONG WITH A SET OF INDEX SPACES ♦ A STORED TABLE AND ALL OF IT’S ASSOCIATED INDEXES MUST BE IN A SINGLE DATABASE ♦ WHEN YOU CREATE A TABLESPACE OR TABLE AND DO NOT SPECIFY THE DATABASE THE OBJECT WILL BE CREATED IN THE DEFAULT DATABASE DSNDB04
  • 17. DB2 STORAGE GROUPS STORAGE GROUP 1 VOLUME 1 VOLUME 2 ♦ USER AND SYSTEM DATABASES ARE PHYSICALLY STORED IN THE DATASETS OF SPECIFIED STORAGE GROUPS ♦ STORAGE GROUP IS A SET OF VOLUMES OF DIRECT ACCESS STORAGE DEVICES(DASD). ♦ PARTS OF SINGLE DATABASE CAN BE STORED IN DIFFERENT STORAGE GROUPS ♦ DEFAULT STORAGE GROUP IS SYSDEFLT
  • 18. TABLE SPACES TABLESPACE 1 TABLE 1 TABLE 2 SIMPLE SEGMENTED PARTITIONED ♦ TABLESPACE IS MADE UP OF ONE OR MORE VSAM LINEAR DATASETS (LDS ), WHERE ONE OR MORE TABLES ARE STORED. ♦ A TABLE SPACE IS DIVIDED INTO 4K OR 32K PAGES. ♦ A PAGE IS A UNIT OF I/O TRANSMISSION. ♦ A PAGE MAY CONTAIN ONE OR MORE ROWS (MAX 127). ♦ A ROW MUST LIE WITHIN A PAGE.
  • 19. Table Spaces A TABLE SPACE can be thought of as a logical address space on secondary storage that is to hold one or more stored tables. Table spaces are divided into equal sized units called PAGES which are written or read from DASD. Tables are physically stored in one or more VASM linear datasets. A table space can consists of 1 to 64 VSAM datasets which can together contain up to 64 GIGABYTES of data. When you create a table space you can specify the database and storage group to which the tablespace belongs and table space type. As the amount of data in tables grow storage will be acquired from appropriate storage groups and added to the tablespace. Fundamentally the table space is a storage unit for recovery and reorganization. If the table space is very large the RECOVERY and REORGANIZATION could take a long time. Hence making the tablespace simple, segmented, or partitioned can drastically affect the performance.
  • 20. SIMPLE TABLESPACE SIMPLE TABLESPACE FREE PAGE FREE SPACE 4K PAGE RECORD OF TABLE 1 RECORD OF TABLE 2 ♦ SIMPLE TABLESPACE CONTAINS ONE OR MORE TABLES ♦ RECORDS OF DIFFERENT TABLES ARE STORED IN AN INTERLEAVED MANNER. ♦ IMPROVE ACCESS TIME FOR LOGICALLY RELATED DATA
  • 21. Simple Tablespace In simple table space records of tables are interleaved .Records of different tables may be present in a single page and to find all rows of a table a scan of the whole table space is needed. But by loading the data in an appropriately interleaved manner; accessing logically related data will be more efficient. If a table is dropped, its rows are not deleted. The space occupied by the rows does not become available until the table space is reorganized. All tables in a simple table space must reside in the same user-defined data set or in the same storage group. one stored table per table space is always the most satisfactory arrangement in the case of simple TABLE SPACE.
  • 22. SEGMENTED TABLESPACE SEGMENT1 SEGMENT2 4K PAGE SEGMENT3 TABLE SPACE HAVING A SEGMENT SIZE 4 RECORD OF TABLE 1 RECORD OF TABLE 2 ♦ TABLE SPACE IS DIVIDED INTO A NUMBER OF SEGMENTS. ♦ RECORDS OF DIFFERENT STORED TABLES ARE NOT INTERLEAVED IN A SINGLE SEGMENT. ♦ A SEGMENTED TABLE SPACE CAN CONTAIN ONE OR MORE TABLES. ♦ SEQUENTIAL ACCESS TO A PARTICULAR TABLE IS MORE EFFICIENT.
  • 23. Segmented Tablespace In a SEGMENTED TABLESPACE the tablespace is divided into segments and each segment consists of a logically contiguous set of N PAGES. N must be a multiple of 4 in the range 4 TO 64 and is same for all segments in the table space. The size of the segment is specified while creating the tablespace. Each segment in the segmented tablespace contains rows from only one table. But the tablespace can contain multiple tables, in different SEGMENTS. In order to find a row, it is not necessary to scan the entire table space, but only the segments that contain the table. Hence sequential access to a particular table is more efficient. If a table in a segmented table space is dropped, the space for that table can be reused without performing a reorganization of the table space. A segmented table space can have between 1 AND 32 VSAM linear data sets. the maximum size of a data set in the segmented table space is 2 GIGABYTES and so, the maximum size of a segmented table space is 64 GIGABYTES .
  • 24. PARTITIONED TABLESPACE A—F PARTITION1 G—P PARTITION2 Q—Z PARTITION3 RECORD OF TABLE 1 ♦ A PARTITIONED TABLESPACE CAN CONTAIN ONLY ONE TABLE. ♦ EACH PARTITION CONTAINS A PART OF ONE TABLE. ♦ THE PARTITIONS CAN BE INDEPENDENTLY ASSIGNED TO DIFFERENT STORAGE GROUPS. ♦ IMPROVED DATA AVAILABILITY AND QUERY RESPONSE TIME.
  • 25. Partitioned Tablespace PARTITIONED TABLESPACES are intended for stored tables that are sufficiently large. Partitioned table contains exactly one stored table, partitioned in accordance with value ranges of a particular column or column combination . A partition can be 1, 2, OR 4 GIGABYTES in length, depending on the number of partitions contained in the entire table space. If only one partition is defined on the table space, then its MAXIMUM SIZE IS 4 GIGABYTES. Partitioning a table space provides several advantages for large tables. When DB2 scans data to answer a query it can scan through partitions simultaneously instead of scanning through the entire table from the beginning to end. A utility can work on all partitions simultaneously instead of working on one partition at a time. Also, different utilities can work on different partitions simultaneously. This can significantly reduce the amount of time needed for a utility to finish.
  • 26. TABLES TABLE S KEY COLUMNS S# SNAME STATUS CITY ROWS S1 SMITH 20 LONDON S2 JONES 10 PARIS S3 BLAKE 30 PARIS S4 CLARK 20 LONDON S5 ADAMS 30 ATHENS ♦ A RELATIONAL DATABASE STORES DATA IN THE FORM OF TABLES. ♦ TABLE CONSISTS OF A NUMBER OF RECORDS. ♦ RECORD CONTAINS COLUMNS, ROWS, KEYS etc. ♦ EACH RECORD SHOULD BE CONTAINED IN A SINGLE PAGE BUT A TABLE CAN BE SPREAD OVER PAGES.
  • 27. VIEWS BASE TABLE AS IT EXISTS VIEW AS THE PROGRAM’S STORAGE LOGIC SEES IT. TABLE S VIEW S# SNAME STATUS CITY S# STATUS CITY ♦ A VIEW CAN INCLUDE ALL OR SOME OF THE COLUMNS FROM ONE OR MORE BASE TABLES ♦ VIEWS ARE CREATED FOR BASE TABLES OR VIEWS OR A COMBINATION OF VIEWS AND TABLES. ♦ VIEWS ARE LOGICAL REPRESENTATION OF DATA THAT EXISTS IN BASE TABLES. ♦ VIEWS ARE USED FOR SIMPLICITY AND SECURITY.
  • 28. Views A VIEW is a named table that is represented, not by its own physically separate, distinguishable stored data, but rather by its definition in terms of other named tables. VIEWS are created for base tables or views or a combination of views and tables. When you define a view DB2 stores the definition of the view in the DB2 catalog. Data is physically present in base tables only and not in views. When a view is accessed then data is dynamically retrieved from the base table. Advantages Of Views 1. They provide a certain amount of logical data independence in restructuring the database 2. They allow the same data to be seen by different users in different ways. 3. Automatic security is provided for data that is present in the base table by creating a view in which sensitive data is not visible.
  • 29. INDEX SPACES INDEX SPACE 1 INDEX 1 ♦ ONLY ONE INDEX IS STORED IN AN INDEX SPACE ♦ INDEX SPACE IS AUTOMATICALLY CREATED WHEN THE CORRESPONDING INDEX IS CREATED. ♦ PAGES IN AN INDEX SPACE ARE 4K BYTES IN SIZE. ♦ INDEX SPACE FOR PARTITIONED TABLESPACE ARE PARTITIONED.
  • 30. INDEX INDEX 1 RID VALUE PAGE P T ♦ INDEX CONSISTS OF TWO PARTS ,RECORD ID (RID) AND INDEXED VALUE. ♦ A TABLE CAN HAVE ANY NUMBER OF ASSOCIATED INDEXES. ♦ INDEXES ARE USED TO IMPROVE PERFORMANCE AND IN SOME CASES TO ENSURE UNIQUENESS. ♦ IN THE EXAMPLE INDEX IS USED TO FIND A RECORD (T) IN PAGE P. ♦ DB2 DETERMINES WHETHER TO USE AN INDEX OR NOT
  • 31. Indexes An index contains values from one or more of a table’s columns and a pointer to the record in a data which matches the index value. DB2 will find data more efficiently by scanning the index and following the pointer than by scanning the entire tablespace. Record ID of index has two parts. First part is to identify the page where the record lies and the second part is the byte offset from the bottom of the page identifying the record. Index is structured in ascending or descending sequence on one or more columns. A given value of interest can be located quickly in the index because of their ascending or descending structure. An index created on a table in a partitioned table space is a partitioned index and is divided into multiple index spaces. Indexes are of two types, unique and non unique indexes. A non unique index can reference duplicate values, a UNIQUE INDEX will not. You can create an index any time after you create the table. But creating an index before loading the data provides significant performance advantages. Indexes can be clustered or non clustered. A clustering index is one in which the records are physically stored in data pages in the sequential order of their index values. The index is used to control physical placement of the indexed records. Newly inserted records are physically stored such that the physical sequence of those records in storage closely approximates the logical sequence as defined by the index. In a non clustered index the records will not be in the order of index values. A table can have any number of indexes but it can have only one clustered index. Clustering is extremely important for optimization purpose. The optimizer will try to choose an access path based on the clustering index . For detailed explanation of indexes please refer ‘More about indexes’, chapter 12.
  • 32. ALIASES ♦ AN ALIAS IS AN ALTERNATIVE NAME FOR A TABLE OR VIEW. IT IS A QUALIFIED NAME THAT CAN BE USED BY ANY AUTHORIZATION ID. ♦ AN ALIAS CAN BE DEFINED FOR A TABLE OR VIEW THAT WAS CREATED BY SOME OTHER USER AND FOR WHICH YOU WOULD OTHERWISE HAVE TO USE A FULLY QUALIFIED NAME ♦ ALIASES WERE DESIGNED FOR A DISTRIBUTED ENVIRONMENT TO AVOID HAVING TO REFERENCE THE LOCATION QUALIFIER OF TABLE OR VIEW ♦ ALIAS IS NOT PRIVATE TO THE CREATOR ♦ AN ALIAS CAN BE DEFINED ON AN UNDEFINED NAME. THAT IS THE OBJECT ON WHICH THE ALIAS IS CREATED NEED NOT BE PRESENT AT THE CREATION TIME
  • 33. Aliases Aliases are useful for creating meaningful names for TABLES and VIEWS. ALIASES are created using CREATE ALIAS statement. One user can use an ALIAS created by another user since aliases are not private to the creator EXAMPLE Suppose user ALPHA creates a table called SAMPLE. CREATE TABLE SAMPLE The fully qualified name of the table SAMPLE is ALPHA.SAMPLE and another user BETA can refer to the table sample by its fully qualified name. SELECT * FROM ALPHA.SAMPLE The user BETA can create an alias called ZTEST for the table ALPHA.SAMPLE using create statement. CREATE ALIAS ZTEST FOR ALPHA.SAMPLE And now he can refer to the table SMPLE created by ALPHA by simply referring to the alias ZTEST SELECT * FROM ZTEST Another user GAMMA can also use BETA’S ALIAS ZTEST to refer to ALPHA’S SAMPLE table. SELECT * FROM BETA.ZTEST
  • 34. SYNONYMS ♦ SYNONYMS ARE USEFUL FOR CREATING MORE MEANINGFUL NAME FOR A PERSON USING A TABLE OR VIEW ♦ A SYNONYM IS AN UNQUALIFIED NAME THAT CAN ONLY BE USED BY THE AUTHORIZATION ID THAT CREATED IT. ♦ A SYNONYM IS PRIVATE TO THE USER WHO CREATES IT ♦ SYNONYM CANNOT REFER TO REMOTE TABLE IN A DISTRIBUTED DATA ENVIRONMENT ♦ A SYNONYM CAN ONLY BE DEFINED ON THE NAME OF AN EXISTING TABLE OR VIEW.
  • 35. Synonyms A SYNONYM like an ALIAS is an alternative name for a table. Creating a SYNONYM for a table or view will allow the creator to refer to those tables and views by the more meaningful synonym created by him. EXAMPLE Suppose user ALPHA creates a table called SAMPLE. CREATE TABLE SAMPLE The fully qualified name of the table SAMPLE is ALPHA.SAMPLE and another user BETA can refer to the table sample by its fully qualified name. SELECT * FROM ALPHA.SAMPLE The user BETA can create a SYNONYM called ZTEST for the table ALPHA.SAMPLE using create statement. CREATE SYNONYM ZTEST FOR ALPHA.SAMPLE And now he can refer to the table SAMPLE created by ALPHA by simply referring to the SYNONYM ZTEST SELECT * FROM ZTEST However the user BETA and table ALPHA.SAMPLE must be at the same site. Also the name ZTEST is completely private to the user BETA. Another user GAMMA cannot use the synonym created by BETA and if it wants a synonym it should be created on ALPHA.SAMPLE.
  • 36. DB2 CATALOG DB2 CATALOG CONSISTS OF TABLES WHICH CONTAIN INFORMATION ABOUT OBJECTS DEFINED UNDER THE DB2 SYSTEM . WHEN A NEW TABLE IS CREATED 4 CATALOG TABLES ARE UPDATED . THEY ARE SYSIBM.SYSTABLES , SYSIBM.SYSCOLUMNS . SYSIBM.SYSTABLESPACE , SYSIBM.SYSTABAUTH ♦ EXAMPLES OF CATALOG TABLES • SYSIBM.SYSTABLES CONTAINS INFORMATION OF A TABLE. WHEN A NEW TABLE IS CREATED DB2 INSERTS ONE ROW INTO THIS CATALOG TABLE. • SYSIBM.SYSCOLUMNS CONTAINS INFORMATION ABOUT THE COLUMNS IN A TABLE. THIS TABLE CONTAINS ONE ROW FOR EVERY COLUMN OF EACH ROW IN A TABLE . • SYSIBM.SYSTABLESPACE CONTAINS INFORMATION OF THE TABLE SPACE CREATED. THIS TABLE CONTAINS ONE ROW FOR EACH TABLESPACE. • SYSIBM.SYSTABAUTH CONTAINS INFORMATION OF THE TABLE NAMES AND AUTHORIZATION ID’s WHICH HAVE PRIVILEGES ON THAT TABLE
  • 37. DB2 Catalog The CATALOG in DB2 is a system database that contains information concerning various objects that are of interest to DB2 itself. Examples of such objects are tables, views, indexes, databases, plans, packages, access privileges, and so on. These information is essential, if the system is to able to do it’s job properly. CATALOG itself contains TABLES and you can see the contents of catalog tables using normal query language ( SQL ). When you create, drop or alter any structure, DB2 updates or deletes rows of the catalog that describe the structure. DBA ‘s and application programmers may use catalog tables to determine ♦ Which application plan and packages use which indexes ♦ Which tablespaces, tables and indexes are in a database ♦ An index’s structure, whether unique or clustered or the number of levels present in an index ♦ The amount of physical space used and remaining ♦ Who created an object and who owns it. ♦ Which plans and packages use objects in a database. ♦ Who has authorization to create objects ♦ Which plans and packages use which tables and tables and views ♦ Which synonyms and aliases have been created on tables and views ♦ Who is authorized to execute which plans and packages etc Optimizer component of bind will use catalog information to choose best access strategy.
  • 38. DB2 DIRECTORY DB2 DIRECTORY CONTAINS INFORMATION REQUIRED TO START DB2 AND DB2 USES THE DIRECTORY DURING NORMAL OPERATION. DB2 DIRECTORY CONSISTS OF A SET OF DB2 TABLES STORED IN 5 TABLE SPACES IN SYSTEM DATABASE DSNDB01. ♦ SKELETON CURSOR TABLESPACE (SCT02) CONTAINS PLANS ♦ SKELETON PACKAGE TABLE (SPT01) CONTAINS PACKAGES ♦ LOG RANGE TABLE SPACE (SYSLGRNX) CONTAINS THE RBA (RELATIVE BYTE ADDRESS ) THE LOG DATASET ♦ SYSTEM UTILITIES TABLE SPACE (SYSUTILX) CONTAINS THE INFORMATION ABOUT RUNNING UTILITIES ♦ THE DATABASE DESCRIPTOR TABLE SPACE (DBD01) CONTAINS INTERNAL CONTROL BLOCKS THAT DESCRIBE THE DATABASES EXISTING WITHIN DB2. ♦ CANNOT ACCESS DIRECTORY USING SQL
  • 39. ACTIVE AND ARCHIVE LOGS DB2 RECORDS ALL DATA CHANGES AND SIGNIFICANT EVENTS IN A LOG AS THEY OCCUR DB2 WRITES EACH LOG RECORD TO A DASD DATA SET CALLED THE ACTIVE LOG. WHEN THE ACTIVE LOG IS FULL, DB2 COPIES THE CONTENTS OF THE ACTIVE LOG TO A DASD CALLED THE ARCHIVE LOG ♦ IN THE CASE OF FAILURE DB2 USES LOGS TO RECOVER DATA. ♦ THE ARCHIVE LOG CAN CONSIST OF UP TO 1000 DATA SETS EACH OF WHICH IS A SEQUENTIAL DATA SET.
  • 40. BUFFER POOLS BUFFER POOLS ARE AREAS OF VIRTUAL STORAGE THAT TEMPORARILY STORE PAGES OF TABLE SPACES OR INDEXES. THE DATA REMAINS IN THE BUFFER UNTIL DB2 DECIDES TO USE THE SPACE FOR ANOTHER PAGE ♦ BUFFER POOLS HOLD THE MOST FREQUENTLY ACCESSED DATA. ♦ USING BUFFER POOLS IMPROVE PERFORMANCE. ♦ DB2 ALLOWS TO USE 50 BUFFER POOLS THAT CONTAIN 4KB BUFFERS AND 10 BUFFER POOLS THAT CONTAIN 32KB BUFFERS. ♦ 4KB BUFFER POOLS ARE BP0 TO BP49 ♦ 32KB BUFFER POOLS ARE BP32K TO BP32K9
  • 41. Buffer Pools Buffer pools, also known as virtual buffer pools, are areas of virtual storage used temporarily to store pages of table spaces or indexes. When an application program needs to access a row of a table, DB2 retrieves the page containing that row and places the page in a buffer. If the row is changed, the buffer must be written back to the table space. If the needed data is already in a buffer, the application program will not have to wait for it to be retrieved from DASD. The result is faster performance. DB2 can provide 2 types of buffer pools, 4K and 32K buffer pools. There are fifty 4K buffer pools named BP0, BP1, P49 and ten 32K buffer pools named BP32K, BP32K1, BP32K9. DB2 manages each buffer pools separately . Generally system administrator decides how much memory to allocate for buffer pools. The more memory allocated to buffer pool the more data it can hold and therefore the greater the likelihood that an application request will find the data there.
  • 42. 4. Data Types This chapter describes various data types used in DB2 and their examples. COBOL declarations of the corresponding DATA TYPES are also included. The sub divisions of this chapter are 4.1. Numeric Data 4.1.1. Nulls 4.2. String Data 4.3. Character Format 4.4. Date/Time Data 4.5. Equivalent Cobol Declarations Of Data Types
  • 43. DATA TYPES EVERY COLUMN IN A TABLE IS ASSIGNED A SPECIFIC TYPE AND SIZE OF DATA CATEGORIES OF DATA TYPES NUMERIC DATA STRING DATA DATE / TIME DATA ♦ EACH COLUMN IN A TABLE MUST BE DEFINED ♦ COLUMN DEFINITION MUST INCLUDE THE DATA TYPE AND SIZE ♦ ALL DATA TYPES CAN INCLUDE NULL VALUES.
  • 44. NUMERIC DATA SMALLINT : TWO BYTE BINARY INTEGER , 15 BITS AND SIGN. INTEGER : FOUR BYTE BINARY INTEGER, 31 BITS AND SIGN. DECIMAL (P,Q): PACKED DECIMAL NUMBER HAVING P DIGITS OF WHICH Q DIGITS ARE AFTER THE ASSUMED DECIMAL POINT FLOAT (M) IF M IS BETWEEN 1 AND 21 THEN IT IS SINGLE REAL PRECISION FLOATING POINT AND IT OCCUPIES FOUR BYTES. IT CAN ALSO BE REFERRED AS REAL FLOAT (M) IF M IS BETWEEN 22 AND 53 THEN IT IS SINGLE FLOAT PRECISION FLOATING POINT AND IT OCCUPIES EIGHT BYTES. IT CAN ALSO BE REFERRED AS FLOAT RANGE OF VALUES SMALLINT -32768 to +32767 INTEGER -2147483648 to +2147483647 DECIMAL (P ,Q) MAXIMUM 31 DIGITS 0 < P < 32 AND ( 0 <= Q <= P ) REAL 5.4E-79 to 7.2E+75. FLOAT 5.4E-79 to 7.2E+75. EXAMPLES OF NUMERIC DATA DECLARATION SPKZ DECIMAL(5, 2) DRU SMALLINT HDNR INTEGER
  • 45. NULLS ♦ SQL SYSTEMS LIKE DB2 REPRESENT MISSING INFORMATION IN A COLUMN BY MEANS OF SPECIAL MARKERS CALLED NULLS. ♦ THE PRESENCE OF NULL VALUE IN A COLUMN DEPENDS ON THE COLUMN DEFINITION . ♦ THREE OPTIONS, SPECIFIED IN COLUMN DEFINITION WHICH DEAL WITH NULL VALUES ARE • NOT NULL • NULL • NOT NULL WITH DEFAULT ♦ IF A COLUMN IS DECLARED AS NOT NULL THEN DB2 WILL NOT ALLOW NULL VALUES ON THAT COLUMN ♦ WHEN A COLUMN IS DECLARED AS NULL WHICH IS THE DEFAULT, DB2 WILL ALLOW NULL VALUE ON THAT COLUMN ♦ NOT NULL WITH DEFAULT MEANS THAT THE COLUMN IN QUESTION CANNOT CONTAIN NULLS, BUT IT IS STILL LEGAL TO OMIT A VALUE FOR THE COLUMN EXAMPLES SPKZ DECIMAL(5, 2) NULL DRU SMALLINT NOT NULL HDNR INTEGER NOT NULL WITH DEFAULT
  • 46. Nulls Null values are used in a table when actual values are unknown. Suppose the weight of a part in the SUPPLIER-PARTS DATABASE is null, then it means that (1) The part exists (2) It does have a weight (3) We do not know what the value is In other words we do not know a genuine weight value that can sensibly be put in the weight slot in the row for the part in question. Instead we mark that slot as null and we interpret that mark to mean precisely that we do not know what the real value is. we can insert a null value in the WEIGHT column if it is declared as NULL. But if it is declared as NOT NULL WITH DEFAULT, it is possible to insert a row into the table without specifying a value for WEIGHT column. In that case the column will contain default values corresponding to the column data type. Suppose that NOT NULL is specified for column WEIGHT in the SUPPLIER- PARTS DATABASE, then this will guarantee that every row in table P will always contain a genuine (not null) WEIGHT value. In other words a value must always be provided for column WEIGHT when a row is inserted into the P table. If a given column is allowed to contain nulls and a row inserted into the table with no value provided for that column DB2 will automatically place a null in that position. Suppose that the WEIGHT column in supplier-table database is specified as NULL, then we can insert a row in the table P without specifying a value for WEIGHT. DB2 will automatically put a null value in that column. NOT NULL WITH DEFAULT means the column in question cannot contain nulls but it is nevertheless still legal to omit a value for the column on insert. If a row is inserted and no value is provided for some column to which NOT NULL WITH DEFAULT applies DB2 automatically places one of the following non null default values in that position. ♦ Zero for numeric items ♦ Blanks for fixed length string columns ♦ Empty (zero length string) for varying length string columns ♦ The value of CURRENT DATE or CURRENT TIME or CURRENT TIMESTAMP for variables declared with attributes DATE, TIME or TIMESTAMP.
  • 47. STRING DATA CHARACTER FORMAT CHARACTER(n) : FIXED LENGTH STRING OF n 8 BIT CHARACTERS OCCUPYING N BYTES VARCHAR(n) : VARYING LENGTH STRING UP TO n 8 BIT CHARACTERS OCCUPYING n+2 BYTES . FIRST TWO BYTES ARE USED FOR STORING THE LENGTH OF THE VARIABLE LONG VARCHAR : VARYING LENGTH CHARACTER STRING WHOSE MAXIMUM LENGTH WILL BE DECIDED BY DB2 RANGE OF VALUES CHARACTER(n) : 1 TO 254 VARCHAR(n) : MUST BE LESS THAN PAGE SIZE (4K) LONG VARCHAR : MAXIMUM LENGTH IS DETERMINED BY THE AMOUNT OF SPACE AVAILABLE IN A PAGE EXAMPLES OF CHARACTER DATA REPRESENTATION SPKZ CHAR (20) NUM VARCHAR (60) VAR LONG VARCHAR
  • 48. GRAPHIC FORMAT GRAPHIC(n) : FIXED LENGTH STRING OF N 16 BIT CHARACTERS OCCUPYING 2n BYTES VARGRAPHIC(n) : VARYING LENGTH STRING UP TO N 16 BIT CHARACTERS OCCUPYING 2n+2 BYTES . FIRST TWO BYTES ARE USED FOR STORING THE LENGTH OF THE VARIABLE LONG VARGRAPHIC : VARYING LENGTH 16 BIT CHARACTER STRING WHOSE MAXIMUM SIZE WILL BE DECIDED BY DB2 RANGE OF VALUES GRAPHIC(N) : 1 TO 127 VARGRAPHIC(N) : N MUST BE LESS THAN HALF THE PAGE SIZE (2K) LONG VARGRAPHIC: MAXIMUM LENGTH IS DETERMINED BY THE AMOUNT OF SPACE AVAILABLE IN A PAGE EXAMPLES OF GRAPHIC DATA DECLARATIONS TABKOST GRAPHIC (10) TABIDVARGRAPHIC (80) TEMP LONG VARRRAPHIC
  • 49. DATE / TIME DATA INTERNAL REPRESENTATIONS DATE YYYYMMDD TIME HHMMSS TIMESTAMP YYYYMMDDHHMMSSNNNNNN ♦ DATE IS REPRESENTED AS A SEQUENCE OF EIGHT UNSIGNED PACKED DECIMAL DIGITS OCCUPYING 4 BYTES ♦ TIME IS REPRESENTED AS A SEQUENCE OF SIX UNSIGNED PACKED DECIMAL DIGITS OCCUPYING 3 BYTES ♦ TIMESTAMP IS REPRESENTED AS A SEQUENCE OF 20 UNSIGNED PACKED DECIMAL DIGITS OCCUPYING 10 BYTES EXAMPLES OF DATE TIME DECLARATIONS CCTEMP DATE CCDAT TIME CCSTAMP TIMESTAMP
  • 50. Date / Time Data Columns whose data types are DATE, TIME, OR TIMESTAMP are represented in an internal form that is transparent to the user of SQL. But DATES, TIMES, AND TIMESTAMPS can also be represented by DATE/TIME strings. These are character string representations of date values. When you retrieve date/time values they must be assigned to properly declared character string variables. When a date or time is assigned to a variable, the string format is determined by a precompiler option or subsystem parameter. When a string representation of a datetime value is used in other operations, it is converted to a datetime value. However, this can be done only if the string representation is compatible with the date / time value Example The ISO date format ‘1987-10-12’ is internally stored in 4 bytes. But you must assign a variable with 10 bytes as host variable for retrieving the above date.
  • 51. EQUIVALENT COBOL DECLARATIONS OF DATA TYPES DATATYPE COBOL DECLARATION CCTEMP SMALLINT 01 CCTEMP PIC S9(4) COMP. CCTEMP INT 01 CCTEMP PIC S9(9) COMP. CCTEMP DECIMAL(9,3) 01 CCTEMP PIC S9(6)V9(3) COMP-3. CCTEMP FLOAT(21) 01 CCTEMP COMP-1. CCTEMP FLOAT(53) 01 CCTEMP COMP-2. CCTEMP CHAR(10) 01 CCTEMP PIC X(10). CCTEMP VARCHAR(80) 01 CCTEMP 49 VARLEN PIC S9(4) COMP. 49 CCVAR PIC X(80).
  • 52. 5. SQL Programming IN DB2 operations are done using structured query language. This chapter explains types of SQL and their usage. SQL statements are divided into ♦ DDL Statements ♦ DML Statements ♦ Control Statements
  • 53. SQL PROGRAMMING SQL (STRUCTURED QUERY LANGUAGE ) IS THE LANGUAGE USED TO ACCESS DATA IN DB2 TABLES SQL DDL DML CONTROL STATEMENTS ♦ DDL (DATA DEFINITION LANGUAGE) • CREATE • ALTER • DROP ♦ DML (DATA MANIPULATION LANGUAGE) • SELECT • UPDATE • INSERT • DELETE ♦ CONTROL STATEMENTS • GRANT • REVOKE • COMMIT • ROLLBACK
  • 54. 5.1. DDL Statements Data definition language statements used for creating, changing and dropping DB2 objects. The following sections explain these statements with suitable examples 5.1.1. Create Database 5.1.2. Create Table Space 5.1.3. Create Table 5.1.3.1.Keys 5.1.3.2.Primary Keys 5.1.3.3.Foreign Keys 5.1.4. Create View 5.1.5. Create Index 5.1.6. Alter Table 5.1.7. Drop
  • 55. CREATE DATABASE THE CREATE DATABASE STATEMENT DEFINES A DB2 DATABASE TO THE DB2 SUBSYSTEM. THE NAME MUST NOT START WITH DSNDB AND MUST NOT IDENTIFY AN EXISTING DATABASE IN THIS STATEMENT YOU CAN SPECIFY THE NAME OF BUFFER POOL AND STORAGE GROUP FOR TABLE SPACES AND INDEXES WITHIN THE DATABASE ♦ IF BUFFER POOL IS NOT SPECIFIED IN THE CREATE DATABASE STATEMENT THEN DEFAULT BUFFER POOL USED IS BP0. ♦ IF STORAGE GROUP IS NOT SPECIFIED IN THE CREATE DATABASE STATEMENT THEN DEFAULT STORAGE GROUP USED IS SYSDEFLT. ♦ EXAMPLE CREATE DATABASE "D2110K" BUFFERPOOL BP2 STOGROUP "SGDB2O";
  • 56. CREATE TABLESPACE THE CREATE TABLESPACE STATEMENT ALLOCATES SPACE FOR TABLES. THIS STATEMENT CREATES A SIMPLE, SEGMENTED, OR PARTITIONED TABLE SPACE IN THE SPECIFIED DATABASE. IF DATABASE IS NOT SPECIFIED THEN TABLESPACE IS CREATED IN THE DEFAULT DATABASE DSNDB04 ♦ EXAMPLES 1. CREATE TABLESPACE "S110K10" IN "D2110K" USING STOGROUP "SGDB2O" PRIQTY 100 SECQTY 52 FREEPAGE 0 PCTFREE 5 BUFFERPOOL BP0 LOCKSIZE ANY CLOSE NO SEGSIZE 8; 2. CREATE TABLESPACE "S110L40" IN "D2110L" USING STOGROUP "SGDB2O" PRIQTY 100 SECQTY 52 ERASE NO NUMPARTS 16 FREEPAGE 0 PCTFREE 5 BUFFERPOOL BP2 LOCKSIZE PAGE CLOSE NO;
  • 57. Create Table Space Many parameters can be specified in the CREATE TABLESPACE statement which decides the type of tablespace, the SIZE of VSAM datasets which hold the tables and indexes, the amount and distribution of space left free in the datasets, the amount of data covered by concurrency control locks etc. All of these decisions made during table space creation hold performance implications. If the developer does not specify choices for any of these parameters DB2 will use default values. In the given examples DB2 automatically creates VSAM linear datasets needed for the tablespace within the specified storage group. Each data set will be defined on a volume of the storage group specified in the create tableapace statement. The values specified for PRIQTY and SECQTY determine the primary and secondary allocations for the data set. Erase parameter Indicates whether the DB2-managed data sets for the tablespace are to be erased when they are deleted during the execution of a utility or an SQL statement that drops the table space. ERASE NO does not erase the data sets. ERASE YES erases the data sets. As a security measure, DB2 overwrites all data in the data sets with zeros before they are deleted. FREEPAGE parameter Specifies how often to leave a page of free space when the table space or partition is loaded or reorganized. The default is FREEPAGE 0, leaving no free pages. PCTFREE parameter indicates what percentage of each page to leave as free space when the table is loaded or reorganized. The default is PCTFREE 5. LOCKSIZE parameter Specifies the size of locks used within the table space . For more information please refer chapter 9. NUMPARTS parameter Indicates that the table space will be partitioned and the number of partitions in that tablespace. BUFFERPOOL parameter Identifies the buffer pool to be used for the table space and determines the page size of the table space. CLOSE parameter specifies whether or not the data sets are eligible to be closed when the table space is not being used or the limit on the number of open data sets is reached. CLOSE YES says the dataset is eligible for closing. This is the default. CLOSE NO specifies that the dataset is not eligible for closing. SEGSIZE parameter Indicates that the table space will be segmented and specifies, how many pages are to be assigned to each segment. If SEGSIZE and NUMPARTS parameters are not given, then the table space will be SIMPLE
  • 58. CREATE TABLE CREATE TABLE STATEMENT CREATES A TABLE IN A TABLESPACE. TABLE NAME IS UNIQUE FOR A USER. IF USERA CREATES TABLEA THEN FULLY QUALIFIED NAME WILL BE USERA.TABLEA. USERA CAN SIMPLY USE THE NAME TABLEA BUT OTHER USERS MUST SPECIFY FULLY QUALIFIED NAME EXAMPLES 1. CREATE TABLE D2110L.SP ( ,S# CHAR(5) NOT NULL ,P# CHAR(6) NOT NULL ,QTY INTEGER NOT NULL ,PRIMARY KEY( S# , P# ) ,FOREIGN KEY ( S# ) REFERENCES S, ,FOREIGN KEY ( P# ) REFERENCES P ) IN D2110L.TABSP (2) CREATE TABLE D2110L.SP LIKE D2110K.TAB IN D2110L.TABSP;
  • 59. KEYS ♦ A KEY IS ONE OR MORE COLUMNS THAT ARE IDENTIFIED AS SUCH IN THE DESCRIPTION OF A TABLE, AN INDEX, OR A REFERENTIAL CONSTRAINT. S# SNAME STATUS CITY S1 SMITH 20 LONDON S2 JONES 10 PARIS S3 BLAKE 30 PARIS KEY ♦ A KEY IDENTIFIES A ROW OF DATA ♦ A ROW IN ONE TABLE CAN CARRY THE KEY OF ANOTHER TABLE SO KEYS ARE USED FOR RELATING TABLES ♦ A KEY COMPOSED OF MORE THAN ONE COLUMN IS CALLED A COMPOSITE KEY. A COMPOSITE KEY IS AN ORDERED SET OF COLUMNS OF THE SAME TABLE. ♦ A UNIQUE KEY IS A KEY THAT IS CONSTRAINED SO THAT NO TWO OF ITS VALUES ARE EQUAL.
  • 60. PRIMARY KEY ♦ A PRIMARY KEY IS A UNIQUE KEY THAT IS A PART OF THE DEFINITION OF A TABLE P# PNAME COLOR WEIGHT CITY P1 NUT RED 12 LONDON P2 BOLT GREEN 17 PARIS P3 SCREW BLUE 17 ROME P4 SCREW RED 14 LONDON P5 CAM BLUE 12 PARIS P6 COG RED 19 LONDON PRIMARY KEY ♦ PRIMARY KEY OF A TABLE IS THE UNIQUE IDENTIFIER FOR THAT TABLE ♦ PRIMARY KEY CAN BE COMPOSITE ♦ A TABLE CANNOT HAVE MORE THAN ONE PRIMARY KEY, AND THE COLUMNS OF A PRIMARY KEY CANNOT CONTAIN NULL VALUES. ♦ WHEN A PRIMARY KEY IS DEFINED ON A TABLE, A UNIQUE INDEX MUST BE CREATED ON THAT PRIMARY KEY
  • 61. FOREIGN KEYS ♦ A FOREIGN KEY IS A COLUMN OR COMBINATION OF COLUMNS IN ONE TABLE WHOSE VALUES ARE REQUIRED TO MATCH VALUES OF THE PRIMARY KEY IN SOME OTHER TABLE. TABLE S TABLE SP S# SNAME STATUS CITY S# P# QTY S1 SMITH 20 LONDON S1 P1 300 S2 JONES 10 PARIS S1 P2 200 S2 P1 300 ….. ……… … …… …. …. ….. PRIMARY KEY IN S FOREIGN KEY IN SP ♦ A FOREIGN KEY VALUE REPRESENTS A REFERENCE TO THE ROW CONTAINING THE MATCHING PRIMARY KEY VALUE. ♦ THE TABLE THAT CONTAINS THE FOREIGN KEY IS KNOWN AS THE DEPENDENT TABLE AND THE TABLE THAT CONTAINS THE PRIMARY KEY IS KNOWN AS THE PARENT TABLE. ♦ EACH VALUE OF A FOREIGN KEY MUST BE WHOLLY NULL OR WHOLLY NON NULL. THAT IS IF FOREIGN KEY IS A COMPOSITE KEY THEN ALL COMPONENTS OF THAT KEY MUST BE NULL OR NON NULL, NOT A MIXTURE.
  • 62. CREATE VIEW THE CREATE VIEW STATEMENT CREATES A VIEW ON TABLES OR VIEWS. IF THE VIEW NAME IS UNQUALIFIED THEN THE AUTHORIZATION ID IS THE IMPLICIT QUALIFIER BASE TABLE: S S# SNAME STATUS CITY VIEW : GOOD_SUPPLIERS S# STATUS CITY ♦ IF YOU DO NOT SPECIFY A LIST OF COLUMN NAMES, THE COLUMNS OF THE VIEW INHERIT THE NAMES OF THE COLUMNS OF THE RESULT TABLE OF THE SUB SELECT. EXAMPLE CREATE VIEW GOOD_SUPPLIERS AS SELECT S# , STATUS, CITY FROM S WHERE STATUS > 15 ;
  • 63. CREATE INDEX THE CREATE INDEX STATEMENT CREATES A PARTITIONED OR NON PARTITIONED INDEX AND AN INDEX SPACE. INDEX CAN BE CREATED ON ONE OR MORE COLUMNS. WHEN YOU CREATE UNIQUE INDEX THE KEY CANNOT HAVE DUPLICATE VALUES. UNIQUE INDEX SHOULD BE CREATED FOR A PRIMARY KEY. ♦ EXAMPLES 1. CREATE UNIQUE INDEX D2110K.I11010U1 ON D2110K.S (S#) BUFFERPOOL BP0 USING STOGROUP SGDB2O PRIQTY 40 SECQTY 20 CLOSE NO; 2. CREATE INDEX D2110P.I11010U2 ON D2110N.P (P# DESC) 3. CREATE UNIQUE INDEX D2110L.I11010U3 ON D2110L.SP (S#, P#)
  • 64. ALTER TABLE THE ALTER TABLE STATEMENT CHANGES THE DESCRIPTION OF A TABLE TO ADD MULTIPLE COLUMNS ,CODE MULTIPLE ALTER STATEMENTS. ADDED COLUMNS MUST ACCEPT NULL OR NOT NULL WITH DEFAULT VALUES THIS COMMAND CANNOT BE USED FOR DELETING A COLUMN PRIMARY AND FOREIGN KEYS CAN BE CREATED AND DROPPED USING THIS COMMAND ♦ EXAMPLES 1. ALTER TABLE D2110.P ADD PRICE SMALLINT; 2. ALTER TABLE D2110K.SP FOREIGN KEY(P#) REFERENCES D2110K.P ON DELETE CASCADE; 3 ALTER TABLE D2110K.P PRIMARY KEY(P#); 4 ALTER TABLE D2110K.S DROP PRIMARY KEY(S#);
  • 65. DROP THE DROP STATEMENT DELETES AN OBJECT ALIAS alias name DATABASE database name INDEX index name STOGROUP stogroup name DROP SYNONYM synonym name TABLE table name TABLESPACE table space name VIEW view name PACKAGE collection-id.package-id FREE PLAN ♦ WHEN AN OBJECT IS DROPPED ALL OBJECTS THAT ARE DIRECTLY OR INDIRECTLY DEPENDENT ON THAT OBJECT ARE DELETED ♦ THE OBJECT’S DESCRIPTION IS DELETED FROM THE CATALOG TABLE.
  • 66. Drop The results of dropping various objects are given below. 1. Dropping an alias has no effect on any view or synonym that was defined using the alias. 2. When you drop the database , the database and all of its table spaces, tables, index spaces, and indexes are dropped. 3. Whenever an index is directly or indirectly dropped ,it’s index space is also dropped. 4. When the synonym is dropped, view or alias that defined using the synonym are not dropped. 5. Whenever a table is directly or indirectly dropped, all privileges on the table, all referential constraints in which the table is a parent or dependent, and all synonyms, views, and indexes defined on the table are also dropped. 6. Whenever a table space is directly or indirectly dropped, all tables in the table space are also dropped. 7. Whenever a view is directly or indirectly dropped, all privileges on the view and all synonyms and views that are defined on the view are also dropped. 8. when the package version is dropped, all privileges on the package are dropped and all plans that are dependent on the execute privilege of the package are invalidated.
  • 67. 5.2. DML Statements Data manipulation statements are used for retrieving data from DB2 tables. The following statements together known as data manipulation language. 5.2.1. Select 5.2.1.1.Comparison Operators 5.2.1.2.Select Distinct 5.2.1.3.Multiple Conditions 5.2.1.4.Order By 5.2.1.5.In, Between 5.2.1.6.Partial Search 5.2.1.7.Aggregate Functions 5.2.1.8.Group By 5.2.1.9.Having 5.2.2. Joining Tables 5.2.3. Sub Queries 5.2.4. Union 5.2.5. Insert 5.2.6. Update 5.2.7. Delete
  • 68. DML STATEMENTS SELECT SQL SELECT REQUIRED SEQUENCE SELECT FROM WHERE ORDER BY EXAMPLE Q: GET SUPPLIER NUMBERS AND STATUS FOR SUPPLIERS IN PARIS, IN DESCENDING ORDER OF STATUS QUERY SELECT S# , STATUS -TELLS WHICH COLUMNS TO USE FROM S -TELLS WHICH TABLES TO USE WHERE CITY = ‘PARIS’ -TELLS WHICH ROWS TO USE ORDER BY STATUS DESC ; -TELLS HOW TO SEQUENCE THE RESULT RESULT S# STATUS S3 30 S2 10
  • 69. COMPARISON OPERATORS = EQUAL ^= NOT EQUAL <> NOT EQUAL > GREATER THAN ^> NOT GREATER THAN >= GREATER THAN OR EQUAL < LESS THAN ^< NOT LESS THAN <= LESS THAN OR EQUAL
  • 70. SELECT DISTINCT SELECT DISTINCT IS TO ELIMINATE DUPLICATE ROWS Q : GET PART NUMBERS FOR ALL PARTS SUPPLIED WITH REDUNDANT DUPLICATES ELIMINATED QUERY : SELECT DISTINCT P# FROM SP; RESULT P# P1 P2 P3 P4 P5 P6
  • 71. MULTIPLE CONDITIONS MULTIPLE CONDITION RETRIEVAL AND OR Q1 : GET SUPPLIER NUMBERS AND SUPPLIER NAMES OF SUPPLIERS LOCATED IN LONDON AND HAVING STATUS CODE 20 Q2 : GET SUPPLIER NUMBERS AND SUPPLIER NAMES OF SUPPLIERS WHOSE STATUS IS 10 OR 20. QUERY 1 : SELECT S#, SNAME FROM S WHERE STATUS = 20 AND CITY = ‘LONDON’ ; QUERY 2 : SELECT S#, SNAME FROM S WHERE STATUS = 10 OR STATUS = 20 ; RESULT 1 RESULT 2 S# SNAME S# SNAME S1 SMITH S1 SMITH S4 CLARK S2 JONES S4 CLARK
  • 72. ORDER BY SPECIFY COLUMN NAME AND TELL WHETHER ASCENDING OR DESCENDING SEQUENCE THE DEFAULT SEQUENCE IS ASCENDING QUERY: SELECT P# , ‘ WEIGHT IN GRAMS = ’ , WEIGHT * 454 FROM P ORDER BY 3, P# ; RESULT P# P1 WEIGHT IN GRAMS = 5448 P5 WEIGHT IN GRAMS = 5448 P4 WEIGHT IN GRAMS = 6356 P2 WEIGHT IN GRAMS = 7718 P3 WEIGHT IN GRAMS = 7718 P6 WEIGHT IN GRAMS = 8448
  • 73. IN, BETWEEN IN : TO MATCH ONE OF A LIST OF VALUES BETWEEN: TO SELECT A RANGE OF VALUES CAN USE NOT IN AND NOT BETWEEN Q1 : GET PART NUMBERS , PNAME AND WEIGHT OF PARTS WHOSE WEIGHT IS ANY ONE OF THE FOLLOWING: 12 ,16 ,17 Q2 : GET PART NUMBERS , PNAME AND WEIGHT OF PARTS WHOSE WEIGHT IS IN THE RANGE 16 TO 19 INCLUSIVE QUERY 1 SELECT P# , PNAME , WEIGHT FROM P WHERE WEIGHT IN ( 12 , 16 , 17 ) ; QUERY 2 SELECT P# , PNAME , WEIGHT FROM P WHERE WEIGHT BETWEEN 16 AND 19 ; RESULT 1 RESULT 2 P# PNAME WEIGHT P# PNAME WEIGHT P1 NUT 12 P2 BOLT 17 P2 BOLT 17 P3 SCREW 17 P3 SCREW 17 P6 COG 19 P5 CAM 12
  • 74. PARTIAL SEARCH TO SEARCH ON A SUBSET OF CHARACTERS : LIKE NOT TO SEARCH ON A SUBSET OF CHARACTERS : NOT LIKE QUERY 1 : SELECT S# , SNAME , CITY FROM S WHERE CITY LIKE ‘L%’ ; QUERY 2 : SELECT S# , SNAME , CITY FROM S WHERE SNAME LIKE ‘%S’ ; QUERY 3 : SELECT S# , SNAME , CITY FROM S WHERE CITY NOT LIKE ‘%A%’ ; QUERY 4 : SELECT S# , SNAME , CITY FROM S WHERE CITY LIKE ‘%DON’ ; QUERY 5 : SELECT S# , SNAME , CITY FROM S WHERE SNAME LIKE ‘_L%’ ;
  • 75. RESULT 1 S# SNAME CITY S1 SMITH LONDON S4 CLARK LONDON RESULT 2 S# SNAME CITY S2 JONES PARIS S5 ADAMS ATHENS RESULT 3 S# SNAME CITY S1 SMITH LONDON S4 CLARK LONDON RESULT 4 S# SNAME CITY S1 SMITH LONDON S4 CLARK LONDON RESULT 5 S# SNAME CITY S3 BLAKE PARIS S4 CLARK LONDON
  • 76. AGGREGATE FUNCTIONS COUNT : NUMBER OF VALUES IN THE COLUMN SUM : SUM OF VALUES IN THE COLUMN AVG : AVERAGE OF VALUES IN THE COLUMN MAX : MAXIMUM OF VALUES IN THE COLUMN MIN : MINIMUM OF VALUES IN THE COLUMN Q1 : GET THE TOTAL NUMBER OF SUPPLIERS. Q2 : GET THE TOTAL QUANTITY, AVERAGE QUANTITY, MAXIMUM QUANTITY AND MINIMUM QUANTITY OF PART P2 SUPPLIED QUERY 1 : SELECT COUNT(*) FROM S; QUERY 2 : SELECT SUM (QTY) , AVG (QTY) , MAX (QTY) , MIN (QTY) FROM SP WHERE P# = ‘P2’ ; RESULT 1 RESULT 2 5 1000 250 400 200
  • 77. GROUP BY WITH GROUP BY, A COLUMN FUNCTION RESULTS IN A SINGLE VALUE FOR EACH GROUP Q : FOR EACH PART SUPPLIED GET THE PART NUMBER AND THE TOTAL SHIPMENT QUANTITY FOR THAT PART QUERY : SELECT P# , SUM (QTY) FROM SP GROUP BY P# ; RESULT P# P1 600 P2 1000 P3 400 P4 500 P5 500 P6 100
  • 78. HAVING HAVING IS USED TO GET SOME SPECIFIC ROWS, FROM THE ROWS OBTAINED BY GROUP BY CLAUSE, WHICH SATISFY THE CONDITION GIVEN IN THE HAVING CLAUSE. HAVING IS USED TO ELIMINATE GROUPS JUST AS WHERE IS USED TO ELIMINATE ROWS. Q: GET PART NUMBERS FOR ALL PARTS SUPPLIED BY MORE THAN ONE SUPPLIER QUERY : SELECT P# FROM SP GROUP BY P# HAVING COUNT (*) > 1. RESULT P# P1 P2 P4 P5
  • 79. JOINING TABLES IT IS A QUERY IN WHICH DATA IS RETRIEVED FROM MORE THAN ONE TABLE Q: GET ALL COMBINATIONS OF SUPPLIER AND PART INFORMATION SUCH THAT THE SUPPLIER CITY FOLLOWS THE PART CITY IN ALPHABETICAL ORDER QUERY : SELECT S.* , P.* FROM S , P WHERE S.CITY > P.CITY RESULT S# SNAME STATUS S.CITY P# PNAME COLOR WEIGHT P.CITY S2 JONES 10 PARIS P1 NUT RED 12 LONDON S2 JONES 10 PARIS P4 SCREW RED 14 LONDON S2 JONES 10 PARIS P6 COG RED 19 LONDON S3 BLAKE 30 PARIS P1 NUT RED 12 LONDON S3 BLAKE 30 PARIS P4 SCREW RED 14 LONDON S3 BLAKE 30 PARIS P6 COG RED 19 LONDON
  • 80. SUB QUERIES A SUB QUERY IS A SELECT-FROM-WHERE EXPRESSION THAT IS NESTED INSIDE ANOTHER SUCH EXPRESSION MAXIMUM 15 LEVELS ARE POSSIBLE IN A NESTED SUB SELECT Q: GET SUPPLIER NAMES FOR SUPPLIERS WHO SUPPLY PART P2. QUERY : SELECT SNAME FROM S WHERE S# IN ( SELECT S# FROM SP WHERE P# = ‘P2’ ) ; RESULT SNAME SMITH JONES BLAKE CLARK
  • 81. UNION THE RESULTS OF ONE OR MORE RELATIONS ARE MIXED TO FORM A SINGLE RELATION USING UNION . Q: GET PART NUMBERS FOR PARTS THAT EITHER WEIGH MORE THAN 16 POUNDS OR ARE SUPPLIED BY SUPPLIER S2 QUERY : SELECT P# FROM P WHERE WEIGHT > 16 UNION SELECT P# FROM SP WHERE S# = ‘S2’ ; RESULT P1 P2 P3 P6
  • 82. INSERT THE INSERT STATEMENT INSERTS A NEW ROW INTO THE TABLE. YOU CAN EITHER INSERT VALUES FOR ALL COLUMNS OR OMIT VALUES. BUT OMITTING A A VALUE FOR SOME COLUMN DEPENDS ON THE WAY THE COLUMN WAS DEFINED Q1 : ADD PART P8 (A SPROCKET , COLOR PINK , WEIGHT 14 , CITY NICE ) TO TABLE P Q2 : ADD PART P7 (CITY ATHENS , WEIGHT 24 ) NAME AND COLOR AT PRESENT UNKNOWN. ASSUME THAT THE COLUMNS PNAME AND COLOR ARE CREATED WITH NULL ATTRIBUTE SPECIFICATION. QUERY 1 : INSERT INTO P VALUES ( ‘P8’, ‘SPROCKET’, ‘PINK’, 14, ‘NICE’ ) ; QUERY 2 : INSERT INTO P ( P#, CITY, WEIGHT ) VALUES ( ‘P7’, ‘ATHENS’, 24 ); P# PNAME COLOR WEIGHT CITY … …. … .... ……. P8 SPROCKET PINK 14 NICE RESULT 1 P7 ? ? 24 ATHENS RESULT 2
  • 83. UPDATE THE UPDATE STATEMENT UPDATES THE VALUES OF SPECIFIED COLUMNS IN ROWS OF A TABLE OR VIEW. UPDATING A ROW OF A VIEW UPDATES A ROW OF THE TABLE ON WHICH THE VIEW IS BASED. Q: CHANGE THE COLOR OF PART P1 TO YELLOW , INCREASE IT’S WEIGHT BY 5 , AND SET IT’S CITY TO UNKNOWN. ASSUME THAT THE DEFINITION OF P.CITY ALLOWS NULL VALUES. QUERY : UPDATE P SET COLOR = ‘YELLOW’ , WEIGHT = WEIGHT + 5 CITY = NULL WHERE P# = ‘P1’ ; RESULT P# PNAME COLOR WEIGHT CITY … … … … … P1 NUT YELLOW 17 ? … … … … …
  • 84. DELETE THE DELETE STATEMENT DELETES ROWS FROM A TABLE OR VIEW. DELETING A ROW FROM A VIEW DELETES THE ROW FROM THE TABLE ON WHICH THE VIEW IS BASED. SINGLE ROW DELETE Q1: DELETE SUPPLIER S5 MULTIPLE ROW DELETE Q2 : DELETE ALL SHIPMENTS WITH QUANTITY GREATER THAN 300 QUERY 1 : DELETE FROM S WHERE S# = ‘S5’ ; QUERY 2 : DELETE FROM SP WHERE QTY > 300 ;
  • 85. 5.3. Control Statements Statements other than DDL and DML are explained in this section. They are 5.3.1. Grant 5.3.2. Revoke 5.3.3. Commit 5.3.4. Roll Back
  • 86. CONTROL STATEMENTS GRANT TO PERFORM ANY OPERATION ON ANY OBJECT THE USER MUST HOLD THE APPROPRIATE PRIVILEGE FOR THE OPERATION AND THE OBJECT IN QUESTION . THE GRANT STATEMENT GRANTS PRIVILEGES ON AN OBJECT TO AUTHORIZATION IDS. TABLE PRIVILEGES GRANT SELECT ON TABLE S TO CHARLY ; GRANT SELECT , UPDATE (STATUS , CITY ) ON TABLE S TO JUDY, JACK, JOHN ; GRANT ALL PRIVILEGES ON TABLE S TO PUBLIC ; PACKAGE AND PLAN PRIVILEGES GRANT EXECUTE ON PLAN PLANB TO CHARLY ; COLLECTION PRIVILEGES GRANT CREATE IN EWSK TO JOHN ; DATABASE PRIVILEGES GRANT CREATETAB ON DATABASE DBX TO NANCY ; USE PRIVILEGES GRANT USE OF TABLESPACE DBX.TS76 TO TOM ; SYSTEM PRIVILEGES GRANT CREATEDBC TO ARNOLD ;
  • 87. REVOKE USED TO REVOKE PREVIOUSLY GRANTED PRIVILEGES ON AN OBJECT FROM USERS. GENERAL FORMAT OF REVOKE IS SIMILAR TO THAT OF GRANT. REVOKE CAN BE USED TO REVOKE ALL PRIVILEGES EXPLAINED IN THE GRANT COMMAND EXAMPLES REVOKE SELECT ON TABLE S FROM CHARLY ; REVOKE UPDATE ON TABLE S FROM JOHN ; REVOKE CREATETAB ON DATABASE DBX FROM NANCY ;
  • 88. COMMIT COMMIT OPERATES ON A UNIT OF RECOVERY AFTER EXECUTING THIS STATEMENT ♦ ALL CHANGES WILL BE DONE PERMANENTLY ♦ ROW LOCKS WILL BE RELEASED ♦ DEFAULT COMMIT IS AT PROGRAM TERMINATION ♦ IF AN APPLICATION DETERMINES THAT A UNIT OF WORK IS SUCCESSFUL IT CAN INDICATE THAT TO THE DATABASE MANAGER VIA A COMMIT. THE DATABASE MANAGER CAN MAKE THE CHANGES PERMANENT ♦ CURSORS ARE CLOSED EXCEPT THOSE DECLARED WITH HOLD OPTION EXAMPLE UPDATE TABLE S SET STATUS = 20 WHERE S# = S1; COMMIT;
  • 89. ROLLBACK A UNIT OF WORK IS UNDONE IF ANY ABNORMAL CONDITION OCCURS . WHEN THIS STATEMENT IS EXECUTED ♦ ALL CHANGES IN THAT UNIT OF WORK WILL BE BACKED OUT ♦ ALL LOCKS ARE RELEASED ♦ ALL OPEN CURSORS ARE CLOSED ♦ WHEN YOU ISSUE A ROLLBACK THEN THE DATABASE MANAGER WILL RE-ESTABLISH THE STATE OF THE DATABASE AT THE LAST COMPLETED UNIT OF WORK ♦ ROLLBACK WILL BE DONE EITHER BY THE PROGRAM OR BY THE SYSTEM. EXAMPLE ROLLBACK WORK ;
  • 90. 6. Program Structure This section gives an over view of a DB2 application program .Different sections to be included in an application are explained briefly. 6.1. Host Variables 6.1.1. Declaring Host Variables 6.2. Indicator Variables 6.3. SQLCA 6.4. Cobol Structure Of SQLCA 6.5. SQLCA Return Codes 6.6. SQLCA Warnings 6.7. Important SQL codes 6.8. Static SQL 6.9. Dynamic SQL 6.10. Example For A DB2 Application Program
  • 91. PROGRAM STRUCTURE STRUCTURE OF A PROGRAM THAT ACCESSES DB2 SQLCA HOST VARIABLE DECLARATIONS DECLARE TABLE STATEMENTS DECLARE CURSOR SQL STATEMENTS WITHOUT FETCH OPEN CURSOR FETCH CURSOR CLOSE CURSOR ♦ DIFFERENT SECTIONS TO BE INCLUDED IN A DB2 PROGRAM ARE SHOWN IN THE ABOVE FIGURE. ♦ IF THE HOST LANGUAGE IS COBOL, THEN HOST VARIABLE DECLARATION, SQLCA, AND DECLARE TABLE STATEMENTS SHOULD BE IN THE WORKING STORAGE SECTION AND CURSOR DECLARATIONS SHOULD BE JUST ABOVE THE PROCEDURE DIVISION. ALL OTHER SECTIONS ARE IN PROCEDURE DIVISION.
  • 92. Program Structure Programs that access DB2 are written in a number of host languages - COBOL, PL/1, C , ASSEMBLER , FORTRAN, BASIC etc. These programs can contain SQL statements that retrieves or updates database. The start and end of SQL statements must be indicated by delimiters. The delimiters used in COBOL are EXEC SQL and END-EXEC. SQL statements must be coded with in these delimiters. Even if multiple SQL statements appear sequentially, each SQL statement should be indicated by delimiters. Pre compiler uses delimiters to identify SQL statements from the host language. EXAMPLE OF USING DELIMITERS IN COBOL EXEC SQL UPDATE S SET STATUS = 10 WHERE CITY = ‘ATHENS’ END-EXEC.
  • 93. HOST VARIABLES HOST VARIABLES ARE USED TO IDENTIFY THE SYMBOLIC NAME OF STORAGE, THAT HAS BEEN DECLARED USING THE APPLICATION PROGRAM LANGUAGE DEFINITION STATEMENT SQL STATEMENT SELECT SNAME INTO :TMPNAME WHERE S# = ‘S1’ HOST VARIABLE ♦ HOST VARIABLES ARE OPTIONAL ♦ HOST LANGUAGE VARIABLES IN SQL STATEMENT MUST BE PRECEDED BY A COLON ♦ HOST VARIABLE MUST MATCH COLUMN DATA TYPE ♦ CAN BE USED ANYWHERE A VALUE IS REQUIRED IN AN SQL STATEMENT
  • 94. EXAMPLE(1) ♦ SQL STATEMENT 1 INSERT INTO S ( S#, SNAME ) VALUES ( ‘S6’ , ‘GEORGE’ ) ♦ SQL STATEMENT 2 INSERT INTO S ( S#, SNAME ) VALUES ( :SUPCODE, :SUPNAME ) In SQL statement 1 the values to be inserted are hard coded .Second SQL statement shows the use of host variables in an embedded SQL .This statement could be included in a processing loop with the program’s logic assigning various values to the host variables. EXAMPLE (2) ♦ SQL STATEMENT UPDATE S SET STATUS = STATUS * :PERCENT WHERE S# = :SUPCODE In this example host variables are used to update a table .
  • 95. DECLARING HOST VARIABLES THERE ARE TWO METHODS OF HOST VARIABLE DECLARATION (1) DECLARE HOST VARIABLES IN THE WORKING STORAGE SECTION (2) EXEC SQL INCLUDE (member name which contains all host variable declarations and declare table statements) END EXEC.
  • 96. Declaring Host Variables You can declare all host variables in the working storage section of the COBOL program. The host variable declaration should match with the corresponding column definition The host variable names must not begin with SQL or EXEC. Another method of declaring host variables is using the verb INCLUDE. All the host variables are declared in a partitioned dataset member and that member is included in the source program using verb INCLUDE.
  • 97. INDICATOR VARIABLES INDICATOR VARIABLE INDICATES THE PRESENCE OF NULL VALUE IN A COLUMN SELECT SNAME INTO :SUPNAME:SUPNAMIND FROM S HOST VARIABLE INDICATOR VARIABLE ♦ INDICATOR VARIABLE IS REQUIRED IF THE SELECTED COLUMNS ALLOWS NULL ♦ IF COLUMN CONTAINS NULL VALUE THEN THE INDICATOR VARIABLE IS SET TO NEGATIVE VALUE, HOST VARIABLE IS UNTOUCHED ♦ INDICATOR VARIABLE IS ASSOCIATED WITH A HOST VARIABLE
  • 98. Indicator Variables When the program is to receive a value from a column that allows nulls, the program can get either a value or null. So the program requires two variables, a host variable to receive value and an indicator variable to indicate the presence of null value in the selected column. If DB2 attempts to indicate the presence of a null and the program does not provide an indicator variable an error occurs. If the value returned is null then the null indicator indicates that by a negative value and the value in the host variable remains unchanged. The program should have an indicator variable for each column that allows null. In EXAMPLE1 when the selected column contains a null value then the program logic is coded in such way to tackle it. Example 2 shows that indicator variables are used for UPDATE operations also. Before updating the table, the indicator variable is made negative and DB2 sets the column to null ignoring the value in the host variable. Indicator variable should be declared like you declare a host variable. Data type of an indicator variable is SMALLINT and corresponding cobol declaration is given below 01 SUPNAMIND PIC S9(4) COMP.
  • 99. Examples 1. EXEC SQL SELECT SNAME , CITY INTO :SUPNAME:SUPNAMIND , :PGMCITY FROM S WHERE S# = ‘ S1’ END EXEC. IF SUPNAMIND < 0 PERFORM NONAME-SECTION ELSE PERFORM NAME-SECTION. 2. IF ( some condition ) SUPNAMIND = -1 ELSE SUPNAMIND = 0. EXEC SQL UPDATE S SET SNAME = :SUPNAM:SUPNAMIND WHERE S# = ‘S1’ END EXEC.
  • 100. SQLCA ( SQL COMMUNICATION AREA) THE SUCCESS OR FAILURE OF THE LAST EXECUTED SQL STATEMENT IS DESCRIBED IN SQLCA PROGRAM STATUS OF EXECUTED SQL SQLCA SQL STATEMENTS DB2 ♦ AFTER EACH SQL STATEMENT, SQLCA CODES MUST BE CHECKED BY THE PROGRAM TO FIND WHETHER THE SQL WAS SUCCESSFUL OR NOT ♦ SQLCA IS INCORPORATED IN THE PROGRAM USING INCLUDE STATEMENT.
  • 101. SQLCA The SQL communication area (SQLCA) is a data structure that must be included in any host language program using SQL .The SQLCA provides a way for DB2 to pass feedback about it’s operations to the program .After executing an SQL DB2 returns via the SQLCA ,codes indicating the execution was successful or identifying errors and special conditions. The program can then test for these codes and react according to their content. The SQLCA structure contains variables for a number of codes and messages. Programmers can code the necessary structure(explained in next page) , copy it from a source library or have DB2 generate it. An include statement allows the source program to include SQLCA structure from the copy library and is shown below. EXEC SQL INCLUDE SQLCA END EXEC.
  • 102. COBOL STRUCTURE OF SQLCA 01 SQLCA. 05 SQLCAID PIC X(8). 05 SQLCABC PIC S9(9) COMP-4. 05 SQLCODE PIC S9(9) COMP-4. 05 SQLERRM. 49 SQLERRML PIC S9(4) COMP-4. 49 SQLERRMC PIC X(70). 05 SQLERRP PIC X(8). 05 SQLERRD OCCURS 6 TIMES PIC S9(9) COMP-4. 05 SQLWARN. 10 SQLWARN0 PIC X. 10 SQLWARN1 PIC X. 10 SQLWARN2 PIC X. 10 SQLWARN3 PIC X. 10 SQLWARN4 PIC X. 10 SQLWARN5 PIC X. 10 SQLWARN6 PIC X. 10 SQLWARN7 PIC X. 05 SQLEXT. 10 SQLWARN8 PIC X. 10 SQLWARN9 PIC X. 10 SQLWARNA PIC X. 10 SQLSTATE PIC X(5). ♦ MOST IMPORTANT SQLCA CODES ARE SQLCODE AND SQLWARN0
  • 103. SQLCA RETURN CODES INTEGER CHAR(1) CONDITION SQLCODE SQLWARN0 REQUEST STATUS ERROR <0 FAILED WARNING >0 & <>100 OR ‘W’ SATISFIED WITH SPECIAL CONDITION NOT FOUND +100 DATA NOT FOUND SUCCESS 0 AND ‘ ‘ SUCCESS ♦ IF SQLCODE CONTAINS A NEGATIVE VALUE THEN IT IS AN ERROR ♦ ALL POSITIVE SQLCODES NOT EQUAL TO 100 ARE CONSIDERED WARNINGS ♦ A ‘W’ IN SQLWRN0 INDICATES A WARNING EVEN IF SQLCODE = 0.
  • 104. SQLCA WARNINGS SQL WARNING DESCRIPTION SQLWARN0 THIS FIELD IS BLANK IF ALL SQL WARNINGS FROM SQLWARN1 TO SQLWARNA ARE BLANKS. CONTAINS ‘W’ IF ONE OR MORE SQL WARNINGS CONTAINS W. SQLWARN1 CONTAINS W IF THE VALUE OF A STRING COLUMN WAS TRUNCATED WHEN ASSIGNED TO HOST VARIABLE. SQLWARN2 CONTAINS W IF NULL VALUES WERE ELIMINATED FROM THE ARGUMENT OF A COLUMN FUNCTION SQLWARN3 CONTAINS W IF THE NUMBER OF RESULT COLUMNS IS LARGER THAN THE NUMBER OF HOST VARIABLES. SQLWARN4 CONTAINS W IF A PREPARED UPDATE OR DELETE STATEMENT DOES NOT INCLUDE A WHERE CLAUSE. SQLWARN5 CONTAINS W IF THE SQL STATEMENT WAS NOT EXECUTED BECAUSE IT IS NOT A VALID SQL STATEMENT IN DB2 FOR MVS/ESA.
  • 105. SQLCA WARNINGS….. SQL WARNING DESCRIPTION SQLWARN6 CONTAINS W IF THE ADDITION OF A MONTH OR YEAR DURATION TO A DATE OR TIMESTAMP VALUE RESULTS IN AN INVALID DAY. AN INVALID DAY (FOR EXAMPLE, JUNE 31). INDICATES THAT THE VALUE OF THE DAY WAS CHANGED TO THE LAST DAY OF THE MONTH TO MAKE THE RESULT VALID. SQLWARN7 CONTAINS A W IF ONE OR MORE NON ZERO DIGITS WERE LIMITED FROM THE FRACTIONAL PART OF A NUMBER USED AS THE OPERAND OF A DECIMAL MULTIPLY OR DIVIDE OPERATION. SQLWARN8 CONTAINS A W IF A CHARACTER THAT COULD NOT BE CONVERTED WAS REPLACED WITH A SUBSTITUTE CHARACTER. SQLWARN9 CONTAINS A W IF ARITHMETIC EXCEPTIONS WERE IGNORED DURING COUNT DISTINCT PROCESSING. SQLWARNA CONTAINS A W IF AT LEAST ONE CHARACTER FIELD OF THE SQLCA OR THE SQLDA NAMES OR LABELS IS INVALID DUE TO A CHARACTER CONVERSION ERROR.
  • 106. Important SQL codes -102 LITERAL STRING IS TOO LONG. STRING BEGINS string -107 THE NAME name IS TOO LONG. MAXIMUM ALLOWABLE SIZE IS size -117 THE NUMBER OF INSERT VALUES IS NOT THE SAME AS THE NUMBER OF OBJECT COLUMNS -119 A COLUMN IDENTIFIED IN A HAVING CLAUSE IS NOT INCLUDED IN THE GROUP BY CLAUSE -125 AN INTEGER IN THE ORDER BY CLAUSE DOES NOT IDENTIFY A COLUMN OF THE RESULT -150 THE OBJECT OF THE INSERT, DELETE, OR UPDATE STATEMENT IS A VIEW FOR WHICH THE REQUESTED OPERATION IS NOT PERMITTED -204 name IS AN UNDEFINED NAME -205 column-name IS NOT A COLUMN OF TABLE table-name -303 A VALUE CANNOT BE ASSIGNED TO OUTPUT HOST VARIABLE NUMBER position-number BECAUSE THE DATA TYPES ARE NOT COMPARABLE -401 THE OPERANDS OF AN ARITHMETIC OR COMPARISON OPERATION ARE NOT COMPARABLE -407 AN UPDATE OR INSERT VALUE IS NULL, BUT THE OBJECT COLUMN column-name CANNOT CONTAIN NULL VALUES -501 THE CURSOR IDENTIFIED IN A FETCH OR CLOSE STATEMENT IS NOT OPEN -502 THE CURSOR IDENTIFIED IN AN OPEN STATEMENT IS ALREADY OPEN -503 A COLUMN CANNOT BE UPDATED BECAUSE IT IS NOT IDENTIFIED IN THE UPDATE CLAUSE OF THE SELECT STATEMENT OF THE CURSOR -504 THE CURSOR NAME cursor-name IS NOT DEFINED -540 THE DEFINITION OF TABLE table-name IS INCOMPLETE BECAUSE IT LACKS A PRIMARY INDEX OR A REQUIRED UNIQUE INDEX
  • 107. -551 auth-id DOES NOT HAVE THE PRIVILEGE TO PERFORM OPERATION operation ON OBJECT object-name -603 A UNIQUE INDEX CANNOT BE CREATED BECAUSE THE TABLE CONTAINS ROWS WHICH ARE DUPLICATES WITH RESPECT TO THE VALUES OF THE IDENTIFIED COLUMNS -623 A CLUSTERING INDEX ALREADY EXISTS ON TABLE table-name -661 INDEX index-name CANNOT BE CREATED ON PARTITIONED TABLE SPACE tspace-name BECAUSE THE NUMBER OF PART SPECIFICATIONS IS NOT EQUAL TO THE NUMBER OF PARTITIONS OF THE TABLE SPACE -672 OPERATION DROP NOT ALLOWED ON TABLE table_name -719 BIND ADD ERROR USING auth-id AUTHORITY PACKAGE package-name ALREADY EXISTS -805 DBRM or PACKAGE NAME location-name.collection-id.dbrm- name.consistency -token NOT FOUND IN PLAN plan-name. REASON reason -811 THE RESULT OF AN EMBEDDED SELECT STATEMENT IS A TABLE OF MORE THAN ONE ROW, OR THE RESULT OF THE SUBQUERY OF A BASIC PREDICATE IS MORE THAN ONE VALUE -904 UNSUCCESSFUL EXECUTION CAUSED BY AN UNAVAILABLE RESOURCE. REASON reason-code, TYPE OF RESOURCE resource-type, AND RESOURCE NAME resource-name -911 THE CURRENT UNIT OF WORK HAS BEEN ROLLED BACK DUE TO DEADLOCK OR TIMEOUT. REASON reason-code, TYPE OF RESOURCE resource-type, AND RESOURCE NAME resource-name -913 UNSUCCESSFUL EXECUTION CAUSED BY DEADLOCK OR TIMEOUT. REASON CODE reason-code, TYPE OF RESOURCE resource-type, AND RESOURCE NAME resource-name
  • 108. CODING AIDS WHENEVER STATEMENT EXEC SQL WHENEVER Condition Action END-EXEC ♦ CONDITION: SQLERROR -- NEGATIVE SQLCODE SQLWARNING -- POSITIVE SQLCODE ( NOT +100 ) -- OR SQLWARN0 = ‘W’ NOT FOUND -- SQLCODE = +100 ♦ ACTION: GO TO :SECTA -- CONTROL TRANSFERRED TO STATEMENT LABELED SECTA CONTINUE -- PROGRAM CONTINUES WITH NEXT STATEMENT -- USED TO CANCEL THE EFFECT OF PRIOR WHENEVER ♦ PHYSICAL PLACEMENT OF WHENEVER STATEMENT DETERMINES THE SQL STATEMENTS UNDER IT’S EFFECT ♦ THE USE OF COLON BEFORE THE LABEL IS OPTIONAL ♦ ‘’ GO TO ‘’ AND ‘’ GOTO ’’ ARE EQUIVALENT
  • 109. Whenever Statement WHENEVER statements help programmers to avoid checking SQLCODE after every SQL statement. WHENEVER statements are SQL STATEMENTS that can be embedded in one or more times in the host language program for branching to a paragraph depending on the content of SQLCODE. Each WHENEVER statement applies to all of the SQL statements that follow it in the program listing, regardless of order in which the statements are actually executed. This happens because COBOL precompiler puts appropriate branching instruction after every SQL statement that follows the whenever statement. WHENEVER statements can be used for three different conditions and these are similar to IF THEN statements. IF SQLcode satisfies some condition then the program performs the branching . EXAMPLE EXEC SQL WHENEVER NOT FOUND CONTINUE END-EXEC EXEC SQL WHENEVER SQLERROR PERFORM ERR-SECTION END-EXEC EXEC SQL WHENEVER SQLWARNING PERFORM WARN-SECTION END-EXEC
  • 110. INCLUDE STATEMENT THE INCLUDE STATEMENT INSERTS DECLARATIONS OR CODE INTO A SOURCE PROGRAM. SOURCE PROGRAM SQLCA (TO BE INCLUDED IN SOURCE PROGRAM ) 01SQLCA EXEC SQL 05 SQLCAID PIC X(8). 05 SQLCABC PIC S9(9) COMP-4. INCLUDE SQLCA END-EXEC. ♦ THE INCLUDE STATEMENT INSERTS SOURCE CODE INTO A SOURCE PROGRAM AT PRE COMPILE TIME. ♦ THE INCLUDE STATEMENT CANNOT REFER TO SOURCE STATEMENTS THAT THEMSELVES CONTAIN INCLUDE STATEMENTS.
  • 111. USING CURSORS PROCESSING MULTIPLE ROWS QUERY: SELECT STATUS, CTTY INTO :RANK, :CITY FROM S WHERE STATUS < 30 ; STATUS CITY 2 LONDON 10 PARIS 20 LONDON RANK CITY STATUS CITY 20 LONDON 10 PARIS 20 LONDON RANK CITY STATUS CITY 20 LONDON 10 PARIS 20 LONDON RANK CITY
  • 112. Processing Multiple Rows In previous example the result of the query gives multiple rows. But there is no method to determine the number of rows satisfying the condition before actually receiving data from DB2.Therefore it is not possible to allocate storage in the application program to receive an entire set of data. When we are using host variables for retrieving data and if the result is a single row the query will work and SQL return code will be set to zero. But in the given example the result of the query gives multiple rows and the host language can deal with only at a time Now the program is in error, SQLCODE will be set to a negative value and the values of the host variables will be unpredictable. DB2 provides the use of cursors to process SETS of data. The cursor is used to retrieve all rows in the SET one by one. Each fetch of the cursor retrieves the next row in the set of data that meets the condition.
  • 113. SELECT WITH FETCH ♦ DEFINE A CURSOR EXEC SQL DECLARE CURSOR K10 FOR SELECT SNAME, CITY DEFINITION FROM S WHERE STATUS < 30 END-EXEC ♦ OPEN THE CURSOR EXEC SQL OPEN K10 END-EXEC ♦ FETCH RESULT ROWS ONE AT A TIME EXEC SQL EXECUTION FETCH K10 INTO :SUPNAME, :CITY END-EXEC ♦ CLOSE CURSOR WHEN FINISHED EXEC SQL CLOSE K10 END-EXEC ♦ THE DECLARE CURSOR STATEMENT RELATES A CURSOR TO A SELECT STATEMENT ♦ OPEN CURSOR STATEMENT GENERATES EXECUTABLE CODE. ♦ FETCH CURSOR STATEMENT RETRIEVES A ROW FROM A SET OF DATA ♦ CLOSE CURSOR STATEMENT DEACTIVATES THE CURSOR
  • 114. Select With Fetch DECLARE cursor statement defines a cursor with the specified name with an associated query as specified by the select that forms part of that declare. The declare cursor statement is not an executable code, but a purely declarative statement. A program can use any number of DECLARE CURSOR statements, and each of which must be of a different name. Open cursor statement generates executable code. The select clause used in the DECLARE CURSOR statement is effectively executed when the cursor is opened. This is done using the current value of the host variable (if used). This executable code will allow subsequent fetch statements to access the set of data that meets the definition of the DECLARE CURSOR‘s underlying SELECT statement. Opening the cursor is a must and DB2 will not open it on the first fetch. The FETCH statement will retrieves a row of data from the set made accessible by the open statement. Data is retrieved in host variables specified after the INTO clause of FETCH statement. After the first FETCH statement which retrieves the first row, the cursor will be advanced to the next row during the second FETCH operation and then assigns values from that row to host variables. After retrieving the required rows the CURSOR can be closed. The CLOSE CURSOR statement releases the cursor from the set of data.
  • 115. UPDATE USING A CURSOR EXEC SQL DECLARE CURSOR K10 FOR SELECT SNAME, CITY FROM S WHERE STATUS = :RANK FOR UPDATE OF CITY END-EXEC EXEC SQL OPEN K10 END-EXEC EXEC SQL FETCH K10 INTO :SUPNAME, :CITY END-EXEC EXEC SQL UPDATE S SET CITY = :NEWCITY WHERE CURRENT OF K10 END-EXEC EXEC SQL CLOSE K10 END-EXEC ♦ DECLARE CURSOR HAS AN ADDITIONAL FOR UPDATE OF CLAUSE. ♦ DECLARE, OPEN, FETCH and CLOSE CURSOR LOGIC IS NOT CHANGED ♦ UPDATE WHERE CURRENT OF cursor name UPDATES THE ROW PRESENTLY IDENTIFIED BY THE CURSOR
  • 116. Update Using A Cursor The usual logic of cursors is used for updating a row which is present in the set of data, satisfying the select statement in the DECLARE CURSOR. The columns that may be updated are specified using FOR UPDATE OF clause in the DECLARE CURSOR statement. The update operation is done after fetching a row from the SET of data. This type of update is useful where the retrieved row is required for the program before updating it. UPDATE WHERE CURRENT OF CURSOR clause updates the row where the cursor is presently positioned. The next row can be updated only after issuing another FETCH. Requirement of specifying FOR UPDATE OF clause for updating a table using CURSORS depends on the pre compiler option given. If pre compiler NOFOR option is specified then FOR UPDATE OF clause is not required. If NOFOR is not specified FOR UPDATE OF CLAUSE is required and an attempt to update a column not mentioned in that column will fail at run time.
  • 117. DELETE USING A CURSOR EXEC SQL DECLARE CURSOR K10 FOR SELECT SNAME, CITY FROM S WHERE STATUS = :RANK FOR UPDATE OF CITY END-EXEC EXEC SQL OPEN K10 END-EXEC EXEC SQL FETCH K10 INTO :SUPNAME, :CITY END-EXEC EXEC SQL DELETE FROM S WHERE CURRENT OF K10 END-EXEC EXEC SQL CLOSE K10 END-EXEC ♦ THE DECLARE, OPEN, FETCH and CLOSE CURSOR LOGIC IS NOT CHANGED ♦ DELETE WHERE CURRENT OF cursor DELETES THE ROW PRESENTLY POSITIONED BY THE CURSOR ♦ THIS FORM OF DELETE WILL BE USED IF THE DATA CONTAINED IN A ROW IS NEEDED BY THE APPLICATION BEFORE IT IS DELETED.
  • 118. STATIC SQL PLAN TO SELECT DATA PROGRAM PLAN * SELECT CALL SELECT RESULT DB2 TABLE • PROGRAM HANDLES THE RESULT ♦ STATEMENT PROGRAMMER KNOWS THE SQL STATEMENT TO BE USED AND ALWAYS DOES THE SAME FUNCTION ON THE SAME TABLES AND COLUMNS. ♦ BIND • ON ALL SQL STATEMENTS • BEFORE PROGRAM EXECUTION • BUILDS A STORED PLAN ♦ AUTHORIZATION • HELD BY THE PLAN BINDER
  • 119. DYNAMIC SQL PLAN TO EXECUTE USER’S REQUEST PROGRAM PLAN PREPARE DB2 EXECUTE CALL EXECUTE TABLE RESULT PROGRAM HANDLES THE RESULT ♦ STATEMENT SQL STATEMENTS ARE PREPARED AT RUN TIME AND EXECUTED. TARGET TABLE OR COLUMN CAN BE SPECIFIED AT RUN TIME ♦ BIND • ON SINGLE STATEMENT • AT STATEMENT EXECUTION • ACCESS STRATEGY NOT SAVED ♦ AUTHORIZATION • HELD BY THE PROGRAM EXECUTOR
  • 120. Example For Dynamic SQL 01 STMT 49 LEN PIC S9(4) COMP. 49 TEXT PIC X(200). 01 X PICX(6). 01 Y PICX(6). 01 Z PIC X(6). …………… …………… …………… EXEC SQL DECLARE SS STATEMENT END-EXEC EXEC SQL DECLARE CC CURSOR FOR SS END-EXEC …………… …………… MOVE WS-TEXT TO TEXT: MOVE LENGTH-OF-TEXT TO LEN (SELECT CL1,CL2,CL3 FROM T1 WHERE CL1 = 1932) EXEC SQL PREPARE SS FROM :STMT END-EXEC EXEC SQL OPEN CC END-EXEC EXEC SQL FETCH CC INTO :X, :Y, :Z END-EXEC ( repeat fetch until sqlcode 100) ………………… …………………. EXEC SQL CLOSE CC END-EXEC
  • 121. Example For A Db2 Application Program IDENTIFICATION DIVISION. ****************************************************************** * IDENTIFICATION DIVISION. * * * ****************************************************************** PROGRAM-ID. SXD11018. ****************************************************************** * * ****************************************************************** ENVIRONMENT DIVISION. ****************************************************************** * * * ENVIRONMENT DIVISION. * * * ****************************************************************** CONFIGURATION SECTION. ****************************************************************** * * CONFIGURATION SECTION. * * * ****************************************************************** SPECIAL-NAMES. DECIMAL-POINT COMMA. INPUT-OUTPUT SECTION. ****************************************************************** * * * INPUT-OUTPUT SECTION. * * * ****************************************************************** FILE-CONTROL. DATA DIVISION. ****************************************************************** * * * DATA DIVISION. * * * ****************************************************************** FILE SECTION. ****************************************************************** * * * FILE SECTION. * * ***********************************************************
  • 122. WORKING-STORAGE SECTION. ****************************************************************** * * * WORKING-STORAGE SECTION. * * * ****************************************************************** *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- * * DB2-COMMUNICATION-AREA DECLARATIONS * *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- EXEC SQL INCLUDE SQLCA END-EXEC. *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- * * SQL-TABLE DECLARATIONEN * *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- EXEC SQL INCLUDE VT11018 ( OUTPUT OF DCLGEN ) END-EXEC. / ……………………………………………………………… ………………………………………………………………( WORKING STORAGE VARIABLES ) ……………………………………………………………… LINKAGE SECTION. ****************************************************************** * LI N KAG E S E CT I O N * ****************************************************************** * …………………………………………………………………. ………………………………………………………………… …………………………………………………………
  • 123. *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- * * SQL-CURSOR DECLARATIONS * *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- EXEC SQL DECLARE T11018_ALL_ROW CURSOR FOR SELECT TAB_INDEX , DAHWV , DAHWB , DART FROM VT11018 ORDER BY TAB_INDEX END-EXEC. PROCEDURE DIVISION ****************************************************************** * * * PROCEDURE DIVISION * * * ****************************************************************** * ****************************************************************** ****************************************************************** * ………………………………………………………. ………………………………………………………. ……………………………………………………… / ****************************************************************** 8100-OPEN-T11018-CURSOR SECTION. ****************************************************************** EXEC SQL OPEN T11018_ALL_ROW END-EXEC ****************************************************************** ……………………………………………………………. …………………………………………………………….
  • 124. …………………………………………………………….. ……………………………………………………………… 8100-FETCH-T11018-ROW SECTION. ( THIS SECTION SHOULD BE IN A LOOP TO FETCH ALL ROWS) ****************************************************************** EXEC SQL FETCH T11018_ALL_ROW INTO :TAB-INDEX , :DAHWV , :DAHWB , :DART END-EXEC ****************************************************************** …………………………………………………………. …………………………………………………………… ………………………………………………………………… ……………………………………………………………. 8100-CLOSE-T11018-CURSOR SECTION. ****************************************************************** EXEC SQL CLOSE T11018_ALL_ROW END-EXEC STOP RUN.
  • 125. 7. Program Preparation This chapter explains the steps involved in executing a db2 application program. Control information required for each step and examples are also provided The topics discussed in this chapter are 7.1. Steps In Program Preparation 7.2. DCLgen (Declarations Generator ) 7.3. Precompile 7.4. Bind 7.4.1. Binding A DBRM To A Package 7.4.2. Binding An Application Plan 7.5. Compile And Linkedit 7.6. Overview Of DB2 Application Program Preparation And Execution 7.7. Associating Load Modules And Packages
  • 126. PROGRAM PREPARATION STEPS IN PROGRAM PREPARATION DCLGEN PROGRAM PRE COMPILE BIND COMPILE AND LINK EDIT EXECUTION DB2 APPLICATION PROGRAM SHOULD GO THROUGH ALL THE ABOVE STEPS.
  • 127. DCLGEN (DECLARATIONS GENERATOR ) INPUT OUTPUT DECLARE TABLE STATEMENT CONTROL STATEMENTS WHICH INCLUDE TABLE OR DCLGEN VIEW NAME AND NAME OF THE HOST LANGUAGE HOST LANGUAGE DATA STRUCTURE DCLGEN USES DB2 CATALOG TABLES ♦ DCLGEN SHOULD BE DONE BEFORE PRE COMPILING THE SOURCE MODULE ♦ DCLGEN GENERATES BOTH DECLARE TABLE STATEMENT AND DATA STRUCTURE IN THE SPECIFIED HOST LANGUAGE. ♦ DECLARE TABLE STATEMENT USED FOR APPLICATION PROGRAM DOCUMENTATION AND PRELIMINARY SYNTAX CHECKING FOR THE PRE COMPILER ♦ USE DCLGEN OR CODE DECLARE TABLE AND HOST LANGUAGE DATA STRUCTURE MANUALLY
  • 128. DCLGEN (Declarations Generator ) The DECLARATIONS GENERATOR supplied with DB2 produces DECLARE TABLE statements for tables and views. It also generates host language data structure that corresponds to the DB2 tables and views to be accessed by the program. The output of DCLGEN will be created in a partition dataset member This member should be included in the working storage section of the application program using INCLUDE statement. The purpose of having DECLARE TABLE statement in the source code is to allow the pre compiler to check the syntax of the SQL statements referring to the tables and views. Having the table and view declarations in the source code allows the pre compiler to uncover syntactical errors, which otherwise would not be found until DB2 binds the plan or package. Host language data structure produced by DCLGEN, is the HOST LANGUAGE DECLARATIONS of tables or views. These can be used as host variables in the application program. DCLGEN prevents us from manually coding host variable declarations and declare table statements.
  • 129. EXAMPLE INPUT FOR DCLGEN DCLGEN TABLE(S) LIBRARY(NTCI.PTAB.DCL(S)) ACTION(REPLACE) LANGUAGE(COBOL) STRUCTURE(S) QUOTE OUT PUT FROM DCLGEN IN NTCI.PTAB.DCL(S) ****************************************************************** * DCLGEN TABLE(S) * * LIBRARY(NTCI.PTAB.DCL(S)) * * ACTION(REPLACE) * * LANGUAGE(COBOL) * * STRUCTURE(S) * * QUOTE * * IS THE DCLGEN COMMAND THAT MADE THE FOLLOWING * STATEMENTS * ****************************************************************** EXEC SQL DECLARE S TABLE (S# CHAR(5) NOT NULL, SNAME CHAR(20),NOT NULL WITH DEFAULT STATUS SMALLINT NOT NULL WITH DEFAULT, CITY CHAR(15) NOT NULL WITH DEFAULT ) END-EXEC ****************************************************************** * COBOL DECLARATION FOR TABLE VT11010 * ****************************************************************** 01 S. 10 S# PIC X(5). 10 SNAME PIC X(20). 10 STATUS PIC S9(4) COMP. 10 CITY PIC X(15). ****************************************************************** * THE NUMBER OF COLUMNS DESCRIBED BY THIS DECLARATION IS 4* ******************************************************************
  • 130. PRECOMPILE SOURCE MODULE SOURCE LISTING DIAGNOSTICS PRE COMPILE CROSS REFERENCES MODIFIED SOURCE CODE DBRM (CONTAINS (CONTAINS CONSISTENCY CONTOKEN ) TOKEN) ♦ PRE COMPILER INPUT HOST LANGUAGE PROGRAM WHICH CONTAINS SQL STATEMENTS ♦ SQL STATEMENTS ARE COMMENTED OUT ARE REPLACED BY HOST LANGUAGE CALL STATEMENTS ♦ PRE COMPILER OUTPUT • MODIFIED SOURCE CODE WHICH CONTAINS PRE COMPILER CONSISTENCY TOKEN (CONTOKEN) WHICH IS AN INTERNAL REPRESENTATION OF TIMESTAMP. • DATABASE REQUEST MODULE WHICH CONTAINS EDITED FORM OF SQL STATEMENTS AND CONSISTENCY TOKEN • ERROR MESSAGES AND OTHER DIAGNOSTIC INFORMATION
  • 131. Pre Compile DB2 application programs include SQL statements and you cannot compile those programs until you change the SQL statements into the language recognized by your compiler. Hence you must use a pre compiler whose function is to analyze the host language source module, stripping all SQL statements it finds and replacing them by host language call statements. PRE COMPILER also creates a DBRM from the SQL statements it encountered. DBRM communicates your SQL requests to DB2 during BIND process. One DBRM is created for a program, the name of the DBRM and program will be the same. DBRM contains SQL statements and host variable information extracted from the source program. The DBRM also contains a consistency token that identifies the program and ties the DBRM to the modified source statements by using the same consistency token present in the modified source code. The pre compiler does a syntax checking using the definition given by the DECLARE TABLE statement on all SQL statements in the program. Pre compiler gives error , warnings and other diagnostic messages depending on the result of syntax checking .
  • 132. BIND DBRMS DIRECTLY BOUND TO THE PLAN INPUT OUTPUT DBRM1 BIND PLAN DBRM2 DBRMS BOUND TO THE PACKAGE AND PACKAGES BOUND TO THE PLAN DBRM1 BIND PACKAGE1 BIND PLAN DBRM2 BIND PACKAGE2 ♦ THERE ARE TWO TYPES OF BIND • BIND PACKAGE • BIND PLAN
  • 133. BIND ♦ BIND CONVERTS HIGH LEVEL SQL STATEMENTS PRESENT IN DBRM TO EXECUTABLE MACHINE INSTRUCTION ♦ BIND THE DBRM TO A PLAN OR PACKAGE BEFORE EXECUTING THE APPLICATION PROGRAM. ♦ BIND INVOLVES • CHECKING THE STATUS OF THE REFERENCED OBJECTS TO DETERMINE IF AN SQL STATEMENT IS EXECUTABLE • CREATING AN OPTIMIZED FORM OF THE SQL STATEMENTS FOR IMPROVED PERFORMANCE AND COMPACTNESS • IDENTIFYING MOST EFFICIENT PATH FOR EACH SQL STATEMENT • BIND CHECKS THE AUTHORIZATION TO PERFORM OPERATIONS REQUESTED BY THE SQL STATEMENT ♦ THE CONSISTENCY TOKEN PRESENT IN THE DBRM WILL BE CARRIED FORWARD TO PACKAGE AND PLAN
  • 134. Bind The out put of the precompiler contains extracted SQL statements from the source module. But DB2 has to do the syntax checking and should determine the best access strategy for each SQL. DB2 records all these information in the PACKAGE. If a DBRM is thought of as an ‘SQL source module’ then the package produced by binding that DBRM can be thought of as the corresponding object module. In other words, a package consists of a set of internal control structures , representing the compiled form of the original SQL statements in the corresponding DBRM Each package is assigned to exactly one collection when it is bound. When you bind a package, you specify the collection to which the package belongs. The collection is not a physical entity, and you do not create it; the collection name is merely a convenient way of referring to a group of packages. Usually all of the packages used in a given application would be assigned to the same collection There are two types of bind. First method is to bind DBRMS to an application plan. In the second method DBRMS are bound to the package and packages to the PLAN. Plan contains pointers to the packages. Bind examines the SQL statements in the input DBRM an checks whether all the necessary elements of a statement are present and syntactically correct. It also checks that the individual binding the plan is authorized to perform the operations requested by the SQL statement. Optimizer component of bind interrogates catalog tables, chooses the access path and generates the machine code calls needed to execute the statement.
  • 135. BINDING A DBRM TO A PACKAGE DBRM CATALOG PACKAGE BIND LISTING DIAGNOSTICS PACKAGE ♦ EACH PACKAGE CONTAINS ONLY ONE DBRM. ♦ PACKAGES ARE OPTIONAL, ALL MEMBERS CAN BE DIRECTLY BOUND TO A SINGLE PLAN ♦ INPUT TO THE PACKAGE BIND IS DBRM AND OUTPUT IS THE PACKAGE. ♦ PACKAGE MUST BE BOUND TO THE PLAN ♦ CON-TOK FROM THE DBRM WILL BE CARRIED ON TO PACKAGE
  • 136. Binding A DBRM To A Package Bind Package Is Explained Using The Following Example BIND PACKAGE (EWSK) - MEMBER (SXD11010) - OWNER (AM1240) - QUALIFIER (SYSADMK ) - VALIDATE (BIND) - EXPLAIN (NO) - ISOLATION (CS) - RELEASE (COMMIT) - ACTION (REPLACE) When you BIND a package specify the collection to which the package belongs. The collection is not a physical entity and you do not create it. In the example collection name is EWSK and the package name produced by this bind is EWSK.SXD11010 The owner of the package is AM1240.The owner of an object has all privileges on that object. If no value is entered the default is the use of the primary AUTHID of the binder. The qualifier parameter will be used as the qualifier of all unqualified tables and views referenced in the application program. Validate parameter is used to specify the method DB2 will use to validate the package or plan. Validation can be performed during bind or when the program runs, indicated by the choices of BIND or RUN with the VALIDATE parameter. VALIDATE (RUN) is the default value. EXPLAIN indicates whether to provide information to the user about the access strategy decided by the bind. Default is EXPLAIN(NO) ACTION parameter indicates whether the package is new or a replacement. ACTION (ADD) will result in an error if the object already exists. The default value of REPLACE will add the object or replace it if it already exists. ISOLATION specifies the locking strategy while using cursors. Default is RR (repeatable read) , can be over ridden using CS (cursor stability): For more information on ISOLATION parameter please refer chapter 9 RELEASE parameter indicates when the locks should be released while using a cursor.
  • 137. BINDING AN APPLICATION PLAN LIST OF PACKAGES OR DBRMS OR BOTH PLAN BIND LISTING DIGNOSTIC MESSAGES PLAN ♦ DBRMS CAN BE BOUND TO A PLAN ♦ A LIST OF PACKAGES CAN BE BOUND TO A PLAN ♦ DBRMS AND PACKAGES TOGETHER CAN BE BOUND TO A SINGLE APPLICATION PLAN ♦ PLAN CONTAINS POINTERS TO THE PACKAGES
  • 138. Binding An Application Plan BIND PLAN IS EXPLAINED USING THE FOLLOWING EXAMPLE BIND PLAN (A610 ) - MEMBER(W41600, w710009) - OWNER(SYSADM) - QUALIFIER(SYSADM) - PKLIST(EWS.A61000 - EWS.SXD11053 , - EWSA.ANLZDB2) - ACTION(REPL) RETAIN - VALIDATE(BIND) - ISOLATION(CS) - CACHESIZE(0) In the above example name of the plan is A610, two DBRMS, and three packages are bound to the plan. Parameters used in this example have the same meaning as in the bind package statement. The parameter ACTION indicates whether a new package is to be added or replaced. ACTION(REPL)RETAIN can be used only for BIND PLAN. RETAIN parameter preserves EXECUTE privileges when you replace the plan. If RETAIN is specified then those users who had been using the plan earlier will have the authority to use it after the bind. Determines the size (in bytes) of the authorization cache acquired in the EDM pool for the plan. At run time, the authorization cache stores user IDs authorized to run. Consulting the cache can avoid a catalog lookup for checking authorization to run the plan.
  • 139. COMPILE AND LINKEDIT MODIFIED SOURCE MODULE (CONTAINS CONTOKEN) COMPILER OBJECT MODULE OTHER LINK EDITOR OBJECT MODULES LOAD MODULE (CONTAINS CONTOKEN) ♦ MODIFIED SOURCE FROM THE PRE COMPILER IS COMPILED USING HOST LANGUAGE COMPILER WHICH PRODUCES OBJECT MODULE. ♦ LINKAGE EDITOR IS USED TO MAKE AN EXECUTABLE LOAD MODULE WHICH CONTAINS MAIN PROGRAM, SUB PROGRAMS, LANGUAGE INTERFACE ROUTINES, AND SYSTEM ROUTINES. ♦ TIMESTAMP PRESENT IN THE MODIFIED SOURCE IS CARRIED ON TO THE LOAD MODULE
  • 140. OVERVIEW OF DB2 APPLICATION PROGRAM PREPARATION AND EXECUTION SOURCE MODULE MODIFIED SOURCE PRECOMPILER DBRM MODULE COMPILER BIND OBJECT PACKAGE MODULE OTHER LINKAGE OBJECT LIST OF BIND EDITOR MODULES PACKAGES LOAD LOAD MODULE APPLICATION MODULE PLAN PLAN / PACKAGES MAIN MEMORY
  • 141. ASSOCIATING LOAD MODULES AND PACKAGES CT CT PRE COMPILE MODIFIED SOURCE DBRM CT CT LOAD MODULE PLAN CONTOKENS SHOULD MATCH TO EXECUTE
  • 142. Associating Load Modules And Packages During PRECOMPILE a CONSISTENCY TOKEN is placed in both the modified source and the DBRM. When DBRM is directly bound to the plan then the CONSISTENCY TOKEN is carried on to the plan from the DBRM. When DBRM is bound to the package then the same CONSISTENCY TOKEN will be present in the package and plan contains pointers to the package. An executable load module can be linked to it’s plan or package using the CONSISTENCY TOKEN field present in them. CONSISTENCY TOKEN is used to ensure that the resultant load module and package were derived from the same original source. Assume that the plan of an application program contains only DBRMS. When this program executes the CONSISTENCY TOKEN present in the load module and the corresponding DBRM should be the same . Otherwise the program will not be executed and gives an SQLCOSE OF -805. Now the DBRM of an application program is bound to the package and a set of packages are bound to the plan. When this program is executed the load module and the package which the program wants to execute should have the same CONSISTENCY TOKEN, failure of this will give an SQLCODE -805.
  • 143. 8. Security Features DB2 provides data integrity by using different security mechanisms. Data access is controlled by using authorization ID’s and privileges given to that ID. This chapter briefly explains these security features and DB2’s referential integrity support. 8.1. Privileges 8.2. Referential Integrity 8.2.1. DB2 Enforcement Of Referential Integrity 8.2.2. Referential Integrity Enforcement Rules 8.2.3. Example For Referential Integrity Violation 8.3. Database Recovery In Case Of Failure 8.3.1. Unit Of Recovery 8.3.2. Data Recovery
  • 144. SECURITY FEATURES ♦ SECURITY IN DATABASE MEANS THE PROTECTION OF ALL OBJECTS IN DATABASE AGAINST UNAUTHORIZED DISCLOSURE, ALTERATION OR DESTRUCTION. ♦ DB2 USES TWO INDEPENDENT FEATURES TO PROVIDE SECURITY TO IT’S OBJECTS • THE AUTHORIZATION SUB SYSTEM • THE VIEW MECHANISM ♦ THE SYSTEM ADMINISTRATOR PROVIDES AUTHORIZATION ID’S TO IT’S USERS. THIS ID IS USED TO LOG ON TO THE SYSTEM AND THE ACTIVITIES USER CAN PERFORM IN DB2 DEPENDS ON THE PRIVILEGES GRANTED TO THIS ID. ♦ THERE ARE TWO TYPES OF AUTHORIZATION ID’S • PRIMARY AUTHORIZATIONS IDS • SECONDARY AUTHORIZATION IDS ♦ VIEW MECHANISM CAN BE USED TO PROTECT SENSITIVE DATA FROM USERS BY CREATING A VIEW ON COLUMNS OF THE BASE TABLE THAT ARE NOT SENSITIVE. NOW THE USER ARE ALLOWED TO USE THIS VIEW , PROTECTING SENSITIVE DATA.
  • 145. Security Features Authorization ID’S are provided to users of DB2 to prevent unauthorized use of DB2 objects. Users are known to DB2 by this authorization identifier given by the system administrator and it is user’s responsibility to identify themselves to by supplying that ID when they sign on to the system. Two types of authorization ID’s DB2 uses to control and track system utilization are primary and secondary AUTHIDs. Each individual is assigned a PRIMARY AUTHID that is used to sign on to the system. Generally it is the primary authorization ID that identifies a process in DB2. When unqualified tables, views, indexes are used in the application program, this AUTHID becomes the qualifier of the object. The operations which can be performed by this AUTHID depends on the privileges granted to it by system administrator or other users. System administrator may provide a secondary authid to a group of developers who need a set of privileges associated with that id. Now the user has all the privileges of both primary and secondary authid. The secondary authorization ID is optional . A user can use DB2 under either a primary AUTHID or secondary AUTHID or both. Suppose you are using primary id and want to shift to secondary authid for some operation to perform . This shift can be achieved by using the command SET CURRENT SQLID = ‘ (name of secondary id)’.
  • 146. PRIVILEGES ♦ SYSTEM ADMINISTRATOR DECIDES WHICH SPECIFIC PRIVILEGE SHOULD BE GIVEN TO WHICH SPECIFIC USERS ♦ DATABASE ADMINISTRATOR HAS IMPLICIT RIGHT TO GRANT OR REVOKE PRIVILEGES FROM THE USER. ♦ DATABASE ADMINISTRATOR CAN GIVE INDIVIDUAL OR A COLLECTION OF PRIVILEGES TO USERS ♦ CREATOR OF AN OBJECT HAS IMPLICIT RIGHT TO DROP OR ALTER THE OBJECT • SYSTEM ADMINISTRATOR HAS THE AUTHORITY TO TAKE ANY POSSIBLE ACTION WITHIN THE DB2 SYSTEM. • PRIVILEGES ARE GIVEN AND TAKEN BACK USING GRANT AND REVOKE COMMANDS
  • 147. Privileges SYSTEM ADMINISTRATOR has the authority on all objects in DB2. In order to perform any operation in DB2, the user must hold appropriate privilege for the operation and the object in question, Otherwise the request will be rejected. System administrator grants single or group (bundled) privileges to users. Group of privileges (BUNDLED PRIVILEGES) used in DB2 are shown below SYSADM SYSTEM ADMINISTRATOR AUTHORITY allows the holder to execute any operation that the system supports. SYSCTRL SYSTEM CONTROL AUTHORITY allows the holder to execute any operation, except for operation that access database contents. Example: CREATE STOGROUP DBADM DATABASE ADMINISTRATOR AUTHORITY on a specific database allows the holder to execute any operation that the system supports on the database Example: SELECT, UPDATE etc DBCTRL DATABASE CONTROL AUTHORITY on a specific database allows the holder to execute any operation that system supports except for data manipulation operation Example: RECOVER DATABASE DBMAINT DATABASE MAINTENANCE AUTHORITY on a specific database allows the holder to execute read only maintenance functions on the database Example: DISPLAY DATABASE, START DATABASE etc SYSOPR SYSTEM OPERATOR AUTHORITY allows the holder to carry out console operator functions on the system. Example: STARTING AND STOPPING SYSTEM TRACE ACTIVITIES PACKADM package administrator authority on a specific collection allows the holder to create packages in that collection and gives the holder all package privileges in that collection
  • 148. REFERENTIAL INTEGRITY DB2’S REFERENTIAL INTEGRITY SUPPORT ♦ THERE ARE TWO GENERAL INTEGRITY RULES IN DB2 FOR MAINTAINING DATA INTEGRITY ENTITY INTEGRITY RULE NO COMPONENT OF PRIMARY KEY OF A BASE TABLE IS ALLOWED TO ACCEPT NULLS. REFERENTIAL INTEGRITY RULE REFERENTIAL INTEGRITY RULE STATES THAT ALL NON NULL VALUES OF FOREIGN KEY MUST APPEAR AS A VALUE OF THE PRIMARY KEY OF SOME SPECIFIC TABLE • BY DEFINITION FOREIGN KEY IN ONE TABLE MATCHES A PRIMARY KEY. • A PRIMARY KEY MUST BE UNIQUE AND CANNOT BE NULL • A FOREIGN KEY VALUE MUST MATCH A PRIMARY KEY VALUE OR BE NULL
  • 149. DB2’S Referential Integrity Support Referential integrity consists of a set of rules used in DB2 to provide accuracy , validity or correctness of data in database. Maintaining integrity is of paramount importance and this task is handled by the system rather than the user . For this the system needs to be aware of integrity rules, it should monitor all operations and should ensure that they do not violate any of those rules. DB2 supports ENTITY INTEGRITY RULE by enforcing the programmer to make the column declaration of the primary key not null. If the primary key is composite then all the columns in that composite key should be declared as not null. The justification for this is basically that the primary key values in base tables serve to identify entities in the real world. Primary keys are used for direct row level retrieval and relating one table to another in relational database. Therefore an unknown value in primary column will be meaningless. DB2 enforces that values of a given foreign key must match the values of the corresponding primary key. But the converse is not a requirement. ie the primary key corresponding to some given foreign key might contain a value that currently does not appear as a value of that foreign key. Table which contains the primary key is the parent table and table containing foreign key is the dependent table. This referential integrity rule can be violated during data manipulation like update, delete, insert. DB2 will monitor all operations and it will not allow any violation in referential integrity rules.
  • 150. DB2 ENFORCEMENT OF REFERENTIAL INTEGRITY ♦ DB2 ENFORCES REFERENTIAL CONSTRAINTS WHEN • AN INSERT STATEMENT IS APPLIED TO THE DEPENDENT TABLE • AN UPDATE STATEMENT IS APPLIED TO A FOREIGN KEY OF A DEPENDENT TABLE OR AN UPDATE OF THE PRIMARY KEY OF THE PARENT TABLE • A DELETE STATEMENT IS APPLIED TO A PARENT TABLE ♦ AN INSERT INTO A PRIMARY KEY TABLE CANNOT VIOLATE REFERENTIAL INTEGRITY AND NO CHECKING IS REQUIRED ♦ DELETION OF A FOREIGN KEY VALUE CANNOT VIOLATE REFERENTIAL INTEGRITY AND NO CHECKING IS REQUIRED
  • 151. REFERENTIAL INTEGRITY ENFORCEMENT RULES ♦ INSERT RULE • THE INSERTION OF ANY FOREIGN KEY VALUE IN THE DEPENDENT TABLE IS ALLOWED ONLY IF THE MATCHING VALUE EXISTS IN THE PRIMARY KEY OF THE PARENT TABLE ♦ UPDATE RULE • CHANGES IN THE PRIMARY KEY VALUES ARE ALLOWED ONLY FOR THOSE VALUES THAT DO NOT HAVE MATCHING FOREIGN KEY VALUES • UPDATING A FOREIGN KEY VALUE IS ALLOWED ONLY IF SUCH A VALUE EXISTS IN THE PRIMARY KEY ♦ DELETE RULE • DELETION OF A PRIMARY KEY VALUE WHEN A CORRESPONDING VALUE EXISTS ∗ WILL BE BARRED IF THE FOREIGN KEY CONSTRAINT HAS BEEN SPECIFIED AS RESTRICT ∗ WILL CAUSE DELETION OF THE CORRESPONDING FOREIGN KEY VALUES IF THE CONSTRAINT HAS BEEN SPECIFIED AS CASCADE ∗ WILL SET THE CORRESPONDING FOREIGN KEY VALUES TO NULL IF THE CONSTRAINT HAS BEEN SPECIFIED SET NULL
  • 152. Referential Integrity Enforcement Rules When integrity constraints are in effect, a few data manipulations like INSERT, UPDATE, DELETE) hold the potential for integrity violations or for unpredictable or anomalous results. DB2 detects some of these situations when it attempts to bind SQL statements that result in problems. Instead of completing such a bind, DB2 issues an error message. Insertion of rows containing new primary key values of the parent table do not require checks of associated foreign keys because additions pose no threat to referential integrity. Values added to foreign key columns of depended table through inserts, on the other hand must have corresponding primary key values. Updating the primary key of the parent table will be restricted if matching foreign keys are found in dependent table. While updating the dependent table the new foreign key value must be present in the parent table. Otherwise the request will be rejected. The delete rule of a referential constraint applies when a row of the parent table is deleted. The effect of this delete on dependent tables will dependent on the ON DELETE clause of FOREIGN KEY DEFINITION. The possible specifications of ON DELETE clause are RESTRICT, CASCADE, SET NULL. When the deleting a primary key value, assume that the delete rule is RESTRICT, then the delete is restricted to the case where there are no matching rows in the dependent table. If matching rows exist then the delete request will be rejected. The delete rule CASCADE deletes all matching rows. Ie This deletes the row corresponding to the primary key in parent table and the matching rows in dependent table. For using the delete rule SET NULL the foreign key must have nulls allowed. Here row corresponding to the primary key value in the parent table will be deleted and the foreign key value will be set to null in all matching rows of the primary key in dependent table.
  • 153. Example For Referential Integrity Violation TABLE S TABLE SP S# SNAME STATUS CITY S# P# QTY S1 SMITH 20 LONDON S1 P1 300 S2 JONES 10 PARIS S1 P2 200 S3 BLAKE 30 PARIS S1 P3 400 S4 CLARK 20 LONDON S1 P4 200 S5 ADAMS 30 ATHENS S1 P5 100 S1 P6 100 S2 P1 300 S2 P2 400 S3 P2 200 S4 P2 200 S4 P4 300 S4 P5 400 Consider tables S and SP for explaining the implications of REFERENTIAL INTEGRITY concept PRIMARY KEY; FOREIGN KEY clauses of the create table statements for these tables are given below TABLE SP TABLE S PRIMARY KEY ( S#, p# ) PRIMARY KEY ( S# ) FOREIGN KEY SFK ( S# ) REFERENCES S ON DELETE CASCADE FOREIGN KEY PFK ( P# ) REFERENCES P ON DELETE RESTRICT In this example table S is the parent table and table SP is the dependent table. PFK and SFK are constraint names that will be used by DB2 in diagnostic messages relating to the foreign keys S# and P#. If the user does not specify the name DB2 will create one derived from the name of the first column participating in the foreign key.
  • 154. Four different cases of potential referential integrity violations for these tables are explained below CASE1 An insert on the SP table might introduce a shipment for which there is no matching supplier. For example INSERT INTO SP (S#, P#, QTY ) VALUES ( ‘S20’, ……) ; CASE2 An update on column SP.S# of the SP table might introduce a shipment supplier number for which there is no matching supplier. For example UPDATE SP SET S# = ‘S20’ WHERE….; CASE3 A deletion on the S table might remove a supplier for which there exists a matching shipment. For example DELETE FROM S WHERE S# = ‘S1’ ; CASE4 An update on column S.S# of the S table might remove a supplier for which there exists a matching shipment . For example UPDATE S SET S# = ‘S20’ WHERE S# = ‘S1’ ; In order to enforce referential constraint, the system must deal with all four of these cases.
  • 155. Explanation CASE1 This situation is prevented by the virtue of the fact that SP.S# is a foreign key in table SP matching the primary key S.S# of table S. Such an insert will simply be rejected. But an insert that introduces a shipment for a supplier that does already exist in table S will be accepted. CASE2 In this case also the update will be rejected . But an update that introduces an SP.S# value that does already exist in table S will be accepted. CASE3 This situation is handled by the delete rule CASCADE. In general RESTRICT would mean that the delete will be accepted only if there no such matching shipments. CASCADE would mean that any such matching shipments will de removed anyway. And SET NULL would mean that any such matching shipments will not be removed but will be updated so that they are no longer matching. CASE4 This situation is handled by the implicit update rule restrict, which means that the update will be accepted only If no such matching shipments exist.
  • 156. DATABASE RECOVERY IN CASE OF FAILURE UNIT OF RECOVERY POINT OF NEW POINT OF CONSISTENCY CONSISTENCY OLD DATA UPDATES UPDATED DATA UNIT OF RECOVERY DATA COMMIT POINT OF NEW POINT OF CONSISTENCY CONSISTENCY ABNORMAL TERMINATION DATA UPDATES BACK OUT UPDATES OLD OLD DATA DATA ♦ SUCCESSFUL EXECUTION OF MULTIPLE SQL STATEMENTS MAY BE NECESSARY TO COMPLETE A LOGICAL UNIT OF RECOVERY ♦ THE APPLICATION PROGRAMMER MUST DETERMINE THE LOGICAL UNIT OF RECOVERY ♦ DATABASE RECOVERY IS DONE TO THE LAST POINT OF CONSISTENCY
  • 157. Unit Of Recovery A unit of recovery is the work done by a DB2 for an application, that changes DB2 data from one point of consistency to another. A point of consistency is a time when all recoverable data that an application program accesses is consistent with other data. A unit of recovery begins with the first change to the data after the beginning of the job or following the last point of consistency and ends at a later point of consistency. If failure occurs within a unit of recovery, DB2 backs out any changes to data, returning the data to its state at the start of the unit of recovery; that is, DB2 undoes the work.
  • 158. DATA RECOVERY BACKUP DATA BASE UPDATED DATABASE F COMMIT A I L U UPDATE1 UPDATE2 R E LOG BACKUP RECOVERED DATABASE RESTORE UPDATE LOG
  • 159. Data Recovery Backups are maintained by database administration for the data in DB2 subsystem. Backups may be of the entire database or of one or more tablespaces. In case of failure database recovery is done using these backups. All data changes and other significant activities are recorded in logs by DB2. Database manager may use the backup copies and the logs to re-establish the data base to the last committed unit of work. Changes that were not committed before the failure are not recovered in any case In the given example, the backup is made for a database by DB2. After that the database is changed , and that is made permanent by issuing a commit. Again the application program tries to do another update and before it’s completion a failure occurs Now we want to recover the data in the database. The database is recovered from he backup and the changes that were made in that database till the last commit were done. and the database is restored.
  • 160. 9. Concurrency Objects in DB2 can be used by many users at the same time. This is achieved by the using proper locking system. This chapter explains how DB2 uses these locks and how much control the programmer has over the concurrency in DB2. 9.1. Concurrency 9.2. Locking Strategy 9.3. Lock Sizes And Types 9.4. Acquire Release Parameters 9.5. Isolation Parameter
  • 161. CONCURRENCY ♦ DB2 ALLOWS ANY NUMBER OF USERS TO ACCESS THE SAME TABLE AT THE SAME TIME .THIS IS CALLED CONCURRENCY ♦ DB2 USES A CONCURRENCY CONTROL MECHANISM TO AVOID ERRORS AND INCONSISTENCIES IN DATA WHEN MULTIPLE USERS ACCESS THE SAME DATABASE. ♦ DB2 MANAGES CONCURRENCY CONTROL WITH SEVERAL TYPES OF LOCKS THAT RESTRICT ACCESS TO DATA WHILE THEY ARE BEING USED ♦ CONCURRENCY CONTROL ELIMINATES THE POSSIBILITY OF ONE USER CHANGING DATA WHILE ANOTHER IS IN THE PROCESS OF USING OR CHANGING THEM WHICH CAN LEAD TO ERRORS OR INCONSISTENCIES IN DATA.
  • 162. Concurrency DB2 is a shared system, that is a system that allows any number of users to access the same database at the same time. Any such system requires some kind of concurrency control mechanism to ensure that concurrent transactions do not interfere with each other operation. The absence of such a mechanism will lead to errors and inconsistencies in data DB2 uses locks to control access to same database by multiple users. The basic idea of locking is simple, when a transaction needs an assurance that some object that is interested in, will not change in some unpredictable manner by another user. An exclusive lock on the object will provide this assurance. The effect of the lock is to lock other transactions out of the object, and thereby to prevent them from changing it. The first transaction is thus able to carry out its processing in the certain knowledge that the object in question will remain in a stable state for as long as the transaction wishes to. If a transaction requests a lock that is not currently available, then the transaction simply waits until it gets it. In practice the installation can specify a maximum wait time; If a transaction ever reaches that threshold in waiting for a lock, it times out and the lock request is failed.
  • 163. LOCKING STRATEGY ♦ DB2 DETERMINES IT’S LOCKING STRATEGY FOR EACH PROGRAM WHEN IT BINDS THE APPLICATION PLAN. THE LOCKING STRATEGY DEPENDS ON SEVERAL FACTORS • THE LOCK SIZES DECLARED IN THE LOCKSIZE PARAMETER OF CREATE TABLESPACE STATEMENT • TYPE OF SQL STATEMENTS • THE PRESENCE OF EXPLICIT LOCK TABLE STATEMENTS • THE ACQUIRE AND RELEASE OPTIONS CHOSEN BY THE DEVELOPER AT BIND TIME • THE ISOLATION LEVEL CHOSEN AT BIND TIME. • THE ACCESS PATH CHOSEN
  • 164. Locking Strategy DB2 allows multiple users to access same object at same time, but they are controlled by locks. DB2 selects appropriate locking mechanism based on concurrency control requirements inherent in the application program. They are called implicit locks. In addition to the implicit locking mechanism, DB2 provides certain explicit facilities. These explicit facilities are 1. LOCKSIZE parameter of CREATE TABLESPACE statement. 2. ISOLATION parameter 3. ACQUIRE / RELEASE parameter 4. SQL statement LOCKTABLE. Lock table statement can be coded in the application program to acquire an explicit lock on an object on behalf of the application program. Other parameters are explained in the following pages. Example LOCK TABLE SP IN EXCLUSIVE MODE;
  • 165. LOCK SIZES AND TYPES ♦ THE SIZE (SCOPE) OF A LOCK ON DATA IN A TABLE DESCRIBES THE AMOUNT OF DATA CONTROLLED ♦ THE SIZE IS SPECIFIED IN THE LOCKSIZE PARAMETER OF CREATE TABLESPACE STATEMENT • LOCKSIZE TABLESPACE THIS MEANS THAT ALL LOCKS ACQUIRED ON DATA IN THE TABLE SPACE WILL BE AT THE TABLE SPACE LEVEL • LOCK SIZE TABLE THIS MEANS THAT LOCKS ACQUIRED ON DATA IN THE TABLE SPACE WILL BE AT THE TABLE LEVEL • LOCKSIZE PAGE THIS MEANS THAT LOCKS ACQUIRED ON DATA IN THE TABLE SPACE WILL BE AT TABLE LEVEL • LOCKSIZE ROW THIS MEANS THAT THE LOCKS ACQUIRED ON DATA IN THE TABLE SPACE WILL BE AT THE ROW LEVEL • LOCKSIZE ANY THIS MEANS THAT DB2 WILL DECIDE THE APPROPRIATE PHYSICAL UNIT OF LOCKING FOR THE TABLESPACE ♦ DB2 ALWAYS REQUIRES A TABLE OR TABLESPACE LOCK BEFORE ACCESS TO DATA IS PERMITTED . ♦ DB2 MAY USE TABLE OR TABLESPACE LOCK ALONE TO ACCESS DATA ACCORDING TO THE LOCKSIZE PARAMETER ♦ IF THE LOCKING STRATEGY INCLUDES ROW OR PAGE LOCKING THEN DB2 LOCKS TABLE OR TABLE SPACE BEFORE LOCKING ROW OR PAGE
  • 166. Lock Sizes And Types Proper selection of lock size is important for better performance and concurrency of the database. A locksize of tablespace allows a process to lock the tablespace which controls all tables inside the table space. On the other hand row lock will only lock the row which the application program wants. In a simple tablespace locking table space means locking all tables inside that table space which will reduce concurrency. But a page lock will lock only those rows of tables present in that page and other users can access other rows in that tablespace concurrently. Locking larger or smaller amounts of data allows you to trade performance for concurrency. When you use page or row locks instead of table or tablespace locks concurrency usually improves, meaning better response times .When you use only table or tablespace locks then processing time and storage used is reduced. But concurrency is also reduced , meaning longer response times for some users. For maximum concurrency, locks on a small amount of data held for a short duration are better than locks on a large amount of data held for a long duration of time. However acquiring a lock requires processor time, and holding a lock requires storage. These things should be kept in mind while deciding a lock size.
  • 167. ACQUIRE RELEASE PARAMETERS ♦ ACQUIRE AND RELEASE ARE BIND OPTIONS WHICH WILL DETERMINE WHEN TO ACQUIRE AND RELEASE ITS LOCKS ♦ ACQUIRE ( ALLOCATE ) ACQUIRES THE LOCK WHEN THE PLAN IS ALLOCATED ♦ ACQUIRE (USE ) ACQUIRES THE LOCK WHEN THE OBJECT IS FIRST ACCESSED. ♦ RELEASE (DEALLOCATE) RELEASES THE LOCKS WHEN THE PLAN IS DE ALLOCATED ♦ RELEASE(COMMIT) RELEASES THE LOCK AT THE NEXT COMMIT POINT. IF THE APPLICATION ACCESSES THE OBJECT AGAIN IT MUST ACQUIRE THE LOCK AGAIN
  • 168. ISOLATION PARAMETER ♦ ISOLATION PARAMETER SPECIFIES THE LOCKING STRATEGY FOR CURSORS ♦ THE ISOLATION LEVEL CHOSEN FOR AN APPLICATION CAN IMPACT BOTH THE LOCK STRATEGY AND THE DURATION OF ROW LOCKS ♦ THE ISOLATION LEVEL CAN BE SPECIFIED DURING BIND TIME ♦ DIFFERENT ISOLATION LEVELS ARE • REPEATABLE READ(RR) • READ STABILITY(RS) • CURSOR STABILITY(CS) • UNCOMMITTED READ(UR) ♦ DEFAULT VALUE FOR ISOLATION PARAMETER IS REPEATABLE READ(RR) ♦ ISOLATION SPECIFIES THE DEGREE TO WHICH OPERATIONS ARE ISOLATED FROM THE POSSIBLE EFFECTS OF OTHER OPERATIONS ACTING CONCURRENTLY. ♦ BASED ON THIS INFORMATION, DB2 CHOOSES TABLE AND TABLE SPACE LOCKS AS NONRESTRICTIVE AS POSSIBLE, AND RELEASES S AND U LOCKS ON ROWS OR PAGES AS SOON AS POSSIBLE.
  • 169. Isolation parameter If an SQL statement embedded in a host language program will return multiple rows, the developer must declare in the program a cursor that presents them to the host program one at a time, usually with in a repeatedly executed block. DB2 can handle locking for these cursors using different ISOLATION levels. ISOLATION(RR) Repeatable read: A row or page lock is held for all accessed rows, qualifying or not, at least until the next commit point. If the application process returns to the same page and reads the same row again, the data cannot have changed and no new rows can have been inserted. ISOLATION (RS) Read stability: A row or page lock is held for pages or rows that are returned to an application at least until the next commit point. If a row or page is rejected during stage 2 processing, its lock is still held, even though it is not returned to the application. If the application process returns to the same page and reads the same row again, the data cannot have changed, although additional rows might have been inserted by another application process. A similar situation can also occur if a row or page that is not returned to the application is updated by another application process. If the row now satisfies the search condition, it appears. ISOLATION(CS) Cursor stability: A row or page lock is held only long enough to allow the cursor to move to another row or page. For data that satisfies the search condition of the application, the lock is held until the application locks the next row or page. For data that does not satisfy the search condition the lock is immediately released. ISOLATION(UR) Uncommitted read: The application acquires few locks and can run concurrently with most other operations. But the application is in danger of reading data that was changed by another operation but not yet committed.
  • 170. 10. DB2I (DB2 Interactive ) DB2I is an interactive facility available in DB2 . Almost all of the functions of DB2 are available in DB2I , Which can be used by developers .This chapter contains 10.1. DB2I 10.2. SPUFI
  • 171. DB2I (DB2 INTERACTIVE ) ♦ THE DB2 INTERACTIVE INTERFACE IS A TSO ONLINE APPLICATION WHICH WORKS UNDER THE CONTROL OF ISPF(INTERACTIVE SYSTEM PRODUCTIVITY FACILITY) WHICH IS A SCREEN /DIALOG MANAGER FOR TSO ♦ DB2I PROVIDES OPTIONS FOR ALL THE DB2 FUNCTIONS THAT DEVELOPERS ARE LIKELY TO NEED ♦ DB2 FUNCTIONS THAT ARE AVAILABLE THROUGH DB2I ARE SHOWN IN THE DB2PRIMARY OPTION MENU DB2 PRIMARY OPTION MENU ===> select one of the following db2 functions and press enter 1 SPUFI (Process SQL statements) 2 DCLGEN (Generate SQL and sorce language declarations) 3 PROGRAM PREPARATION (Prepare a DB2 application program to run) 4 PRE COMPILE (Invoke DB2 pre compiler) 5 BIND/REBIND/FREE (Bind rebind or free appl. Plans or packages) 6 RUN (RUN an SQL program) 7 DB2 COMMANDS (Issue DB2 commands) 8 UTILITIES (Invoke DB2 utilities) 9 CATALOG VISIBILITY (Invoke catalog dialogs) d DB2I DEFAULTS (set global parameters) x EXIT ( leave DB2)
  • 172. DB2I DB2 provides a number of commands for use in readying a program for execution that programmers can use to perform the functions required to convert code from source to executable modules. A convenient alternative is to work through DB2I , which provides a menu interface to the necessary command processor . If you develop programs using TSO and ISPF, you can prepare them to run using the DB2 Program Preparation panels. These panels guide you step by step through the process of preparing your application to run. There are other ways to prepare a program to run, but using DB2I is the easiest, as it leads you automatically from task to task. DB2I primary option menu lists the functions it can perform. The user can select any one of these functions according to his requirements SPUFI (SQL processor using file input) supports the online execution SQL statements from a TSO terminal. SPUFI is intended basically for application programmers who wish to perform SQL portions of their programs. The DCLGEN menu allows users to invoke the declarations generator program, which produces the DECLARE TABLE statements and host language data structure. Other options like PRECOMPILE, BIND, RUN are used for preparing and executing DB2 application program. UTILITIES menu helps the user to invoke DB2 online utilities like LOAD, REORG, RECOVER etc. The necessary utility control statements to direct the operation of the specific utility must be created before the utility is invoked.
  • 173. SPUFI INPUT SQL SPUFI OUTPUT STATEMENTS RESULTS DB2 ♦ SPUFI PROCESSES INCLUDE • PREPARING INPUT FILE FOR SPUFI • DB2I SUBMITS THE SQL TO DB2 • SUCCESSFUL JOBS ARE AUTOMATICALLY COMMITTED • EXAMINING THE RESULTS OF SQL
  • 174. 11. Utilities For analyzing and managing physical data present in data base, DB2 offers a number of utilities . This chapter gives a brief explanation of these utilities 11.1. Load 11.2. Runstats 11.3. Reorg
  • 175. UTILITIES DB2 OFFERS A NUMBER OF UTILITIES FOR ANALYZING AND MANAGING THE PHYSICAL STORAGE OF DATA . THERE ARE TWO TYPES OF DB2 UTILITIES. ONLINE UTILITIES STAND ALONE UTILITIES ♦ DB2 ONLINE UTILITIES RUN AS STANDARD MVS BATCH JOBS, AND THEY REQUIRE DB2 TO BE RUNNING ♦ THE STAND-ALONE UTILITIES EXECUTE AS BATCH JOBS INDEPENDENT OF DB2. THEY CAN BE INVOKED ONLY BY MEANS OF MVS JCL. IMPORTANT ONLINE UTILITIES ARE ♦ LOAD ♦ REORG ♦ RECOVER ♦ RUNSTATS IMPORTANT STAND ALONE UTILITIES ARE ♦ DSNJU003 ♦ DSNJU004 ♦ DSN1CHKR
  • 176. LOAD THE LOAD UTILITY LOADS DATA FROM A SEQUENTIAL FILE TO ONE OR MORE TABLES IN A TABLESPACE INPUT LOAD UTILITY CORRECT DATA DB2 TABLE DATA EXAMPLE CONTROL INFORMATION FOR LOAD UTILITY LOAD DATA RESUME NO LOG NO inddn ddname INTO TABLE D2110K.S ( S# POSITION (1) CHAR 5 P# POSITION (6:11) CHAR 6 QTY POSITION (12:15) INTEGER );
  • 177. Load Load utility is used to load data from a sequential file to a TABLE in a table space. In the previous example the TABLE S is loaded from the dataset specified in the load jcl. ddname of the input dataset that is used in the LOAD JCL is given in INDDN parameter. Each fields and their positions are also specified. If the table space already contains data, you can choose whether you want to add new data to existing data or replace the existing data. This can be done using the parameter RESUME. There are three options for RESUME. RESUME NO: Indicates that the dataset is to be empty. This is the default option. RESUME NO REPLACE: This causes the utility to over write the existing data. RESUME YES: This allows the utility to add new rows to the existing table. The LOG NO command instructs the utility not to record data in the log as they are loaded .IF the user does not specify LOG NO , the utility records the changes which can be used for recovery purpose. Default is LOG YES. Recording data in the log during a load can increase the time required for the load significantly.
  • 178. RUNSTATS RUNSTATS UTILITY COLLECTS STATISTICS OF TABLESPACE AND UPDATES CATALOG TABLES RUNSTATS SHOULD BE EXECUTED IMMEDIATELY AFTER A TABLE AND IT’S INDEXES ARE CREATED AND THE DATA IS LOADED DB2 OPTIMIZER CAN TAKE ADVANTAGE OF THESE UPDATED CATALOG TABLES TO SELECT BEST ACCESS STRATEGY EXAMPLE CONTROL INFORMATION FOR RUNSTATS UTILITY RUNSTATS TABLESPACE D2110K.TABSP TABLE(ALL) INDEX(ALL) ;
  • 179. Runstats The RUNSTATS utility reads tablespaces and indexes to collect statistics describing the data. The main statistics collected include number of rows in the table, number of pages that contain the rows of the table, number of distinct values of indexed column , percentage of space occupied by rows etc. RUNSTATS utility uses this information to update CATALOG tables. In the previous example RUNSTATS utility is used for table space TABSP in database D2110K. All tables in the tablespace are specified by TABLE(ALL) keyword. Here you can specify the table name in parentheses after keyword TABLE on which the utility has to run. You can obtain statistics on all indexes on all tables in the named table space by specifying INDEX(ALL).The user can get statistics of one more specific indexes by specifying them in parentheses after the keyword INDEX . The RUNSTATS utility is useful for finding out the free space remaining in a tablespace and we use that information for reorganizing the tablespace.
  • 180. REORG REORG UTILITY IS USED TO REORGANIZES DATA ON PHYSICAL STORAGE OF TABLES. DIFFERENT PHASES OF REORG UTILITY ARE ♦ UNLOADS ROWS FROM A TABLE SPACE ♦ RELOADS ROWS IN A NEATER ARRANGEMENT WITH FREE SPACE ♦ REBUILDS INDEXES ♦ DOES NOT VALIDATE DATA CONTROL STATEMENTS FOR REORG UTILITY REORG TABLESPACE D2110K.TABSP LOG NO;
  • 181. Reorg The REORG online utility reorganizes a table space or index to improve access performance and reclaim fragmented space. In addition, the utility can reorganize a single partition of either a partitioned index or a partitioned table space. REORG utility reorganizes table space or index as you specify in control statements. When an index space only is reorganized then the data pages are not processed. Only leaf pages which contains indexes are scanned. Proper scheduling of reorganizations significantly improves performance of all application programs. In the given example REORG utility is run on tablespace TABSP in database D2110K. If you want to reorganize an index then specify REORG INDEX (index name) . LOG NO parameter is specified in the example to avoid writing data records in the log while loading the tablespace.
  • 182. 12. Advanced DB2 This section explains some of the advanced concepts in DB2. The detailed discussions on indexes and DB2 locks are included. Advanced topics present in this section are 12.1. More About Indexes 12.1.1.Example Of An Index 12.1.2.Clustered Indexes 12.1.3.Non Clustered Indexes 12.2. Special Registers 12.3. More About Locks 12.3.1.Modes Of Table And Tablespace Locks 12.3.2.Modes Of Row And Page Locking 12.3.3.Lock Mode Compatibility Of Table And Table Space Locks 12.3.4.Lockmode Compatibility Of Row And Page Locks 12.4. Invoking Online Utilities
  • 183. More About Indexes DB2 uses indexes not only to enforce uniqueness on column values, as for primary keys, but also to cluster data, partition tables, and to provide access paths to data for queries. Understanding some of the structure of DB2 indexes can be important for achieving your best performance. A table can have more than one index, and an index key can use one or more columns. An index key is a column or an ordered collection of columns on which an index is defined. A composite key is a key built on 2 to 64 columns. The usefulness of an index depends on its key. Columns that you use frequently in performing selection, join, grouping, and ordering operations are good candidates for use as keys DB2 allows you to enter duplicate values in a key column. If you do not want duplicate values, use CREATE UNIQUE INDEX. If a table has a primary key, its entries should be unique. Its uniqueness is enforced by defining a unique index on the primary key columns,
  • 184. EXAMPLE OF AN INDEX 25 61 86 ROOT PAGE 8 17 25 33 40 61 70 75 86 INTER- MEDIATE PAGES LEAF PAGES . . 8 . . 17 . . 25 . . 33 . 40 . . 61 . . 70 . . 75 . . 86 POINTERS TO DATA RECORDS DATA PAGES ♦ THE INDEX IS STRUCTURED AS A B-TREE ♦ A RECORD IS LOCATED USING ROOT PAGE, INTERMEDIATE PAGES AND LEAF PAGES ♦ THE PAGE SIZE OF AN INDEX IS 4KB
  • 185. Example Of An Index Indexes in DB2 are based on a structure known as B-Tree. Indexes can have more than one level of pages. Index pages that point directly to the data in the tables are called leaf pages. If the index has more than one leaf page, it must have at least one non leaf page, containing entries that point to leaf pages. If it has more than one non leaf page, the non leaf pages whose entries point directly to leaf pages are said to be on the first level; there must be a second level of non leaf pages to point to the first, and so on. The highest level contains a single page, called the root page. A typical index is shown in the figure, which is a multilevel, tree structured index with the property that the tree is always balanced, that is that is all leaf entries in the structure are equidistant from the root of the tree. and this property is maintained as new entries are inserted into the tree and existing entries are deleted The root page is the top of the structure. The root page will contain an entry for each non leaf or immediate page. The entry in the root page consists of the high value contained on the intermediate page and a pointer to that page. The immediate pages are similar in structure to the root page, expect that the range of values addressed is more specific. The immediate page contains an entry for each of the leaf pages addressed. The entry consists of the high value contained on the leaf page and a pointer to this leaf page. The leaf pages contain the RID, using which the record can be located in a table space. The leaf pages collectively address the entire table.
  • 186. CLUSTERED INDEXES 25 61 ROOT PAGE 8 17 33 40 INTERMEDIATE PAGES LEAF PAGES DATA PAGES ♦ A CLUSTERING INDEX IS ONE IN WHICH THE RECORDS ARE PHYSICALLY STORED IN DATA PAGES IN THE SEQUENTIAL ORDER OF THEIR INDEX VALUES ♦ HIGH PERFORMANCE BECAUSE OF REDUCED I/O OPERATIONS ♦ EACH TABLE CAN HAVE ONLY ONE CLUSTERING INDEX ♦ CLUSTERING INDEXES ARE EXTREMELY IMPORTANT FOR OPTIMIZATION PURPOSES. OPTIMIZER WILL TRY TO CHOOSE AN ACCESS PATH BASED ON THE CLUSTERING INDEX
  • 187. Clustered Index A clustering index is one for which the sequence defined by the index is the same as or close to the physical sequence. The clustering holds the most potential for performance gains. With a clustering index DB2 takes responsibility for maintaining rows in sequence on the clustering index columns as long as there is free space. DB2 maintains clustering by placing inserted rows in the indexed column’s sequence on available free space in the data pages.DB2 can then process the table in that order efficiently. If it is a non clustering index then DB2 has to reread data pages to identify all the qualifying rows, which will reduce performance. Clustering is valuable when DB2 must process a column’s values in sequence. The SQL statements ORDER BY, GROUP BY, and DISTINCT require such processing. If a column specified in these operation and there is not a suitable index on the column, DB2 must sort it to put it in sequence before returning even one row to the user. If there is a clustering index on that column DB2 uses this column to retrieve the rows in sequence and return the rows immediately one by one. To specify a clustering index, use the CLUSTER clause in the CREATE INDEX statement. CREATE INDEX STATEMENT FOR A CLUSTERED INDEX CREATE UNIQUE INDEX D2110N.I11010U1 ON D2110N.T11010 (TAB_INDEX) BUFFERPOOL BP0 USING STOGROUP SGDB2O PCTFREE 20 FREEPAGE 10 PRIQTY 40 SECQTY 20 CLOSE NO CLUSTER;
  • 188. NON CLUSTERED INDEXES 25 61 ROOT PAGE 8 17 33 40 INTERMEDIATE PAGES LEAF PAGES DATA PAGES ♦ IN A NON CLUSTERED INDEX THE DATA ROWS DO NOT CORRESPOND TO THE ORDER OF THE INDEX ENTRIES
  • 189. SPECIAL REGISTERS ♦ A SPECIAL REGISTER IS A STORAGE AREA THAT DB2 DEFINES FOR A PROCESS ♦ SPECIAL REGISTERS USED IN DB2 ARE • CURRENT DATE • CURRENT DEGREE • CURRENT PACKAGESET • CURRENT RULES • CURRENT SERVER • CURRENT SQLID • CURRENT TIME • CURRENT TIMESTAMP • CURRENT TIMEZONE • USER
  • 190. Special Registers DB2 supports a number of special registers. A special register is a storage area that DB2 defines for a process. Wherever its name appears in an SQL statement, the name is replaced by the register's value when the statement is executed. Thus, the name acts like a function that has no arguments. (zero argument built in scalar functions) You can use the SET statement to change the current value of a register. Where the register's name appears in other SQL statements, the current value of the register replaces the name when the statement executes. A commit or rollback operation has no effect on the values of special registers. Nor does any SQL statement, other than SET statement can change a register value CURRENT DATE, specifies the current date. The data type is DATE. The date is derived by the DB2 that executes the SQL statement that refers to the special register. Example: Display the average age of employees. SELECT AVG(YEAR(CURRENT DATE - BIRTHDATE)) FROM DSN8410.EMP; CURRENT PACKAGESET specifies a string of blanks or the collection ID of the package or packages that will be used to execute SQL statements. The data type is CHAR(18). EXAMPLE Example: For executing a program, identify the collection ID for its package as EWSA. SET CURRENT PACKAGESET = 'EWSA'; CURRENT SQLID specifies the SQL authorization ID of the process. The data type is CHAR(8). This SET statement is used to change the authorization id for a process Example: Set the SQL authorization ID to 'GROUP34' (one of the authorization IDs of the process). SET CURRENT SQLID = 'GROUP34'; CURRENT TIME, specifies the current time. The time is derived by the DB2 that executes the SQL statement that refers to the special register. , Example: Display information about all project activities and include the current date and time in each row of the result. SELECT DSN8410.PROJACT.*, CURRENT DATE, CURRENT TIME FROM DSN8410.PROJACT;
  • 191. CURRENT TIMESTAMP, specifies the current timestamp. The data type is TIMESTAMP. The timestamp is derived by the DB2 that executes the SQL statement that refers to the special register. Example: Display information about the full image copies that were taken in the last week. SELECT * FROM SYSIBM.SYSCOPY WHERE TIMESTAMP > CURRENT TIMESTAMP - 7 DAYS; CURRENT USER specifies the primary authorization ID of the process. The data type is CHAR(8). Example: Display information about tables, views, and aliases that are owned by the primary authorization ID of the process. SELECT * FROM SYSIBM.SYSTABLES WHERE CREATOR = USER;
  • 192. MORE ABOUT LOCKS MODES OF TABLE AND TABLESPACE LOCKS IS INTENT SHARE IX INTENT EXCLUSIVE S SHARE U UPDATE SIX SHARE WITH INTENT EXCLUSIVE X EXCLUSIVE ♦ IS : THE LOCK OWNER CAN READ ANY DATA IN THE TABLE IF AN S LOCK CAN BE OBTAINED ON THE TARGET ROW OR PAGE ♦ IX : THE LOCK OWNER CAN READ OR CHANGE ANY DATA IN THE TABLE PROVIDED AN X LOCK CAN BE OBTAINED ON ROWS OR PAGES TO BE CHANGED AND A U OR S LOCK CAN BE OBTAINED ON ROWS TO BE READ ♦ SIX: THE LOCK OWNER CAN READ ANY DATA IN THE TABLE AND CHANGE ROWS IN THE TABLE PROVIDED IT CAN OBTAIN AN X LOCK ON THE TARGET ROW OR PAGE FOR CHANGE. ROW LOCKS ARE NOT OBTAINED FOR READING. ♦ S : THE LOCK OWNER CAN READ ANY DATA IN THE TABLE AND WILL NOT OBTAIN ROW OR TABLE LOCKS ♦ U : THE LOCK OWNER CAN READ ANY DATA IN THE TABLE AND MAY CHANGE DATA IF AN X LOCK ON THE TABLE CAN BE OBTAINED. NO ROW OR PAGE LOCKS ARE OBTAINED ♦ X : THE LOCK OWNER CAN READ OR UPDATE ANY DATA IN THE TABLE. ROW LOCKS ARE NOT OBTAINED
  • 193. Modes Of Table And Tablespace Locks The locking modes IS IX SIX are used at the TABLE OR TABLESPACE level to support row or page locks. They permit row or page level locking while preventing more exclusive locks on the table by other applications. When an application obtains an IS lock on a table, that application may acquire a lock on a row or page for read only. Other applications can also read the same row. In addition other applications can change data on other rows in the table. An application having an IX lock on a table can change a row after acquiring a row or page lock. Other applications can READ/CHANGE data on other rows in the table. When an application has an SIX lock on a table, that application may acquire a lock on a row for change. Other application can only read other rows in the table. The modes S U and X are used at the table level to enforce the strict table locking strategy. No row or page level locking is used by application that possess one of these locking modes. When an application obtains an S lock on a table, that application can read any data in that table. It will allow other applications to obtain locks that support read only requests for any data in the entire table. No application can change any data in the table until s lock is released. When an application obtains a U lock on a table , that application can read any data from that table and may eventually change data in that table by obtaining an X lock. Other applications can only read data In that table. When an application obtains an X lock on a table that application can read and change any or all data in the table or tablespace . No other application can access data in the entire table or tablespace for READ or CHANGE
  • 194. MODES OF ROW AND PAGE LOCKING ROW/PAGE LOCK MINIMUM SUPPORTING TABLE/TABLE SPACE LOCK S SHARE IS U UPDATE IX X EXCLUSIVE IX ♦ S : THE ROW IS BEING READ BY ONLY ONE APPLICATION AND IS AVAILABLE FOR READ ONLY BY OTHER APPLICATIONS ♦ U : THE ROW IS BEING READ BY ONE APPLICATION BUT IS POSSIBLY TO BE CHANGED BY THAT APPLICATION. THE ROW IS AVAILABLE FOR READ ONLY BY OTHER APPLICATIONS ♦ X : THE ROW IS BEING CHANGED BY ONE APPLICATION AND IS NOT AVAILABLE FOR OTHER APPLICATION ♦ ROW LEVEL LOCKS ARE ONLY REQUESTED BY APPLICATIONS THAT HAVE SUPPORTING LOCKS AT THE TABLE LEVEL
  • 195. LOCK MODE COMPATIBILITY OF TABLE AND TABLE SPACE LOCKS MODE OF MODE OF LOCK B LOCK A IS S IX SIX U X IS YES YES YES YES YES NO S YES YES NO NO YES NO IX YES NO YES NO NO NO SIX YES NO NO NO NO NO U YES YES NO NO NO NO X NO NO NO NO NO NO ♦ THE SYMBOLS A AND B IN THE ABOVE DIAGRAM ARE USED TO REPRESENT TWO DIFFERENT APPLICATIONS ♦ THIS CHART IS USEFUL TO DETERMINE IF TWO APPLICATION CAN RUN CONCURRENTLY IF THEY ARE ACCESSING SAME TABLE WITH THE GIVEN LOCK MODE AT THE SAME TIME.
  • 196. Lock Mode Compatibility Of Table And Table Space Locks If application A obtains an IS lock against a given table application B could obtain an IS, S, IX, SIX or U lock against the same table at the same time. However an X lock would not be permitted at the same time. This particular example illustrates the concept of IS lock acting as supporting lock for a lower level of locking. The only table lock that is not compatible is X lock which would require exclusive lock use of the table. The presence of IS lock indicates that a lower level of locking is required for this table and X lock is not given. Study of the chart reinforces the definitions of table and row lock modes presented on previous pages. Review the row for IX under application A. Assume that application A obtains an IX lock on table Y. This lock indicates that the application intends to obtain locks to support change at the row level. The application will allow other rows to be read and updated but will prevent access to the target rows Examine each of the possible competing table locks that application B might request IS-- Intent to lock for read only at row level. This lock is compatible. There may be contention at the row level if application A is changing the same row that application B wants to read. S-- Share lock at the table level. This lock is not compatible since the S lock states that the entire table is available for read only by the application possessing the lock and all other applications. The IX lock states that an intent to change data at the row level which contradicts the requirement for read only. Therefore application B could not obtain the S lock IX-- Intent to lock for change at the row level. This lock is compatible. There may be lock contention at the row level if application A is changing the same row that application B wants to change. SIX—The SIX lock states that lock request for changing data may be required at the row level for the application processing the lock. In addition the rest of the table is available for read only applications. The IX lock implies change at the row level as well. Application B could obtain six lock on the table U-- Read with intent to update. This table level lock states that the application processing the lock may read any data and may potentially exchange the U lock for an X lock. However until this exchange is done other applications can obtain locks supporting read only. Application B would not be able to obtain the U lock at the same time that application a possessed an IX lock on the same table. X-- The application possessing this mode of lock on the table requires exclusive use of the table. No other access is permitted. The ix lock possessed by an application A would prevent application B from obtaining x lock The same type of statements can be logically derived for the other rows in the chart
  • 197. LOCK MODE COMPATIBILITY OF ROW AND PAGE LOCKS MODE MODE OF LOCK B OF LOCK A S U X S YES YES NO U YES NO NO X NO NO NO ♦ THIS CHART IS USEFUL TO DETERMINE IF TWO APPLICATION CAN RUN CONCURRENTLY IF THEY ARE ACCESSING SAME ROW WITH THE GIVEN LOCK MODE AT THE SAME TIME. ♦ CONSIDER AN APPLICATION A HAVING AN S LOCK ON ROW Y. THEN ANOTHER APPLICATION B CAN ONLY GET LOCKS AND U ON THAT ROW ♦ IF AN APPLICATION A HAS A SHARE LOCK ON A ROW IT, WILL ALLOW OTHER APPLICATIONS TO READ THE SAME ROW. SO APPLICATION B CAN GET AN S LOCK ON THE SAME ROW AT THE SAME TIME ♦ AN APPLICATION B CAN GET AN UPDATE LOCK ON A ROW WHICH IS CURRENTLY LOCKED BY AN S LOCK OF APPLICATION A. IF THE APPLICATION B WANTS TO CHANGE THAT ROW DB2 WILL WAIT UNTIL THE S LOCK IS REMOVED AND IT WILL PROMOTE THE U LOCK TO AN X LOCK. ♦ NO TWO APPLICATION CAN HAVE AN EXCLUSIVE LOCK ON THE SAME ROW AT THE SAME TIME ♦ THE SAME TYPE OF STATEMENTS CAN BE LOGICALLY DERIVED FROM OTHER ROWS OF ABOVE CHART.
  • 198. Invoking Online Utilities Creating utility control statements is the first step required to run an online utility. Utility control statements define the function the utility job performs. Utility control statements are read from the SYSIN input stream. The SYSIN stream can contain multiple utility control statements. Control statements are different for each utility and are explained in chapter 11 There are different methods of invoking DB2 online utilities. Commonly used methods are using DB2I and IBM supplied JCL procedure DSNUPROC. When you use DB2I (DB2 interactive ) panel for executing a utility you must specify the name of the utility , the dataset which contains the control information and other datasets needed by the the utility. Then you can execute the utility from that panel. DB2 on line utilities can be invoked using DSNUPROC procedure, For that you must write and submit JCL, in your JCL, the EXEC statement invokes the DSNUPROC procedure. You must give the control statements as input to DSNUPROC and use the necessary datasets required for the execution of the utility.
  • 199. Sample JCL For Invoking Online Utilities /EX6216X JOB SW301709,'I65000 XT01DL1', // NOTIFY=&SYSUID, // MSGCLASS=8,REGION=6M, // TIME=15,LINES=200 //* //PROCLIB JCLLIB ORDER=NTTU.SYS.PROCLIB //*============================================================= ======== //* °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° //* DB2 LOAD //* °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° //*============================================================= //* //*------------------------------------------------------------------*/ //* T00101 //* -------------------------------------------------------------------- /* //T00101R EXEC DSNUPROC,PARM='DB2O,I650001T001012' //DSNUPROC.SYSIN DD * RUNSTATS TABLESPACE D20015.S001501 TABLE (ALL) INDEX (ALL) /* //*

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