01 dbms-introduction


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01 dbms-introduction

  1. 1. Database Management Systems Overview of Database SystemsDBMS: Overview of DB Systems 1 Dr. Kriengkrai Porkaew
  2. 2. Overview of DB Systems • Objectives and Outline – to study … • The definition of database systems • The importance of database systems • Data abstraction and database models • Database languages • Database system components • Users and creators of database systems • Database products and applications • Database research and trendsDBMS: Overview of DB Systems 2 Dr. Kriengkrai Porkaew
  3. 3. Database Systems: Definition • A Database System (DBS) consists of – A Database (DB) and – A Database Management System (DBMS) – A Database is • a collection of well-organized and interrelated data – A Database Management System is • a set of programs to manipulate those dataDBMS: Overview of DB Systems 3 Dr. Kriengkrai Porkaew
  4. 4. Goals of DBMSs • To provide a way to store and retrieve database information conveniently and efficiently. • DBMSs must meet the following requirements: – Data Persistency • The data must outlast their creators – System Reliability • The system must be able to recover correctly and promptly, if crash – Scalability • The system must be able to handle large numbers of data and lots of usersDBMS: Overview of DB Systems 4 Dr. Kriengkrai Porkaew
  5. 5. Management of Data • DBMSs are responsible for management of data, which involves – defining structures for storing information (DDL) – providing mechanisms for manipulating information (DML) – ensuring the safety of the information stored, despite system crashes (System Reliability) or attempts at unauthorized access (System Security) – avoiding possible anomalous results if / when data are to be shared among several users (Concurrency Control) – supporting large amount of data and concurrent users (Scalability)DBMS: Overview of DB Systems 5 Dr. Kriengkrai Porkaew
  6. 6. The Importance of DB Systems • Before the advent of DB Systems – File systems are used to store data. – File systems do not provide mechanisms for data management – Programmers need to do a lot of data management tasks • Defining data structures • Manipulating data: inserting, searching, updating, deleting • Maintaining data consistency and data integrity • Handling data access permission • Controlling concurrent data accessDBMS: Overview of DB Systems 6 Dr. Kriengkrai Porkaew
  7. 7. File Systems vs. Database Systems File Systems Database Systems Data redundancy Data consistency Difficult data access Simple data access Integrity problem Integrity constraint Atomicity problem Ensure atomicity Concurrent access anomalies Concurrency control Security problem Authorization mechanism Long development Short development Tightly-couple data-program Data independence relationshipDBMS: Overview of DB Systems 7 Dr. Kriengkrai Porkaew
  8. 8. Disadvantages of DB Systems • Do not use a DB system if • Overhead of using a DB – the DBMS does not support system the types of queries or – installation / configuration functionality required by the applications overhead • since the DBMS cannot fulfill • difficult to setup the needs – operating overhead • e.g., presentation, calculation • concurrency control, – transaction support, atomicity and durability persistent storage, and guarantee, etc. many other dominant – price features that the DBMS • hardware, software, provides are not needed maintenance, and support • since the DBMS imposes too high overhead • e.g., data caching, logging 8DBMS: Overview of DB Systems Dr. Kriengkrai Porkaew
  9. 9. Data Abstraction • A major purpose of a database system is to provide users with an abstract view of the data. • The system hides certain details of how the data are stored and maintained. • For ease of use, simple user interfaces are provided to users. • For efficiency, complex data structures are used to represent data in the database.DBMS: Overview of DB Systems 9 Dr. Kriengkrai Porkaew
  10. 10. View of Data • There are multiple levels of data abstraction. • E.g., Data of a person can be viewed as … – High-level: medical records, academic background – Intermediate-level: name (alphabetic), age (numeric), gender (enumeration: Male/Female) – Low-level: sequences of bits, bytes, and blocks • In 1978, “ANSI/SPARC” architecture defines three levels of data abstraction – External Level (View) – Conceptual Level (Logical) – Internal Level (Physical)DBMS: Overview of DB Systems 10 Dr. Kriengkrai Porkaew
  11. 11. ANSI/SPARC Architecture • In ANSI/SPARC Architecture, a database contains – View schemas • describe different views of the database (External Level) – Logical schema • describes the design at the logical level (Conceptual Level) – Physical schema • describes the design at the physical level (Internal Level) • A Schema of a database – Is the overall structures of the data in the database and their relationships – Schemas change infrequently while data change consistently.DBMS: Overview of DB Systems 11 Dr. Kriengkrai Porkaew
  12. 12. Levels of Data Abstraction • View Level – only parts of the entire database • Logical Level – what data are stored in the database and – what relationships exist among those data. • Physical Level – how data are actually storedDBMS: Overview of DB Systems 12 Dr. Kriengkrai Porkaew
  13. 13. DBMS Data Independence • Data Independence – Lower-level schema changes will not effect upper-level schemas and applications • Physical Data Independence – if physical schema changes do not affect application programs. – That is, application programs do not depend on physical schema (but depend on a logical schema or a view schema). • Logical Data Independence – if logical schema changes do not affect application programs. – That is, application programs do not depend on logical schema (but depend on some views).DBMS: Overview of DB Systems 13 Dr. Kriengkrai Porkaew
  14. 14. DB Models and History • 1961, Charles Bachman (1973 Turing Award) designed GE’s Integrated Data Store: IDS – the predecessor of Network Model. • Late 1960s, IBM built “Information Management System: IMS” Hierarchical Model. • Late 1960s, CODASYL group defined/standardized Network Model. • 1969, Relational Model by Edgar Codd [IBM] (1981 Turing Award). • 1970s, SEQUEL (SQL), QBE; QUEL, System R (DB2), Ingres • 1976, Entity-Relationship Model by Peter Chen • 1980s, DB2, Oracle, Sybase, Informix, DBase, Paradox, … • 1986, SQL Standard • 1980s, distributed databases • 1998, James Gray received Turing Award in Transaction Management. • 1990s-2000s, OODB, ORDB (Postgres); Data Warehouse, OLAP, Data Mining, GIS, Mobile DB, Multimedia DB, Web DB, XML DB, …DBMS: Overview of DB Systems 14 Dr. Kriengkrai Porkaew
  15. 15. Data Models • Hierarchical Model • Object-Oriented Model – the first DB model – mostly for special purposes – e.g., IMS, System 2000 – e.g., ObjectStore, Gemstone, • Network Model Ontos, O2, Jasmine, Cache, – DBTG standard; after IDS … – e.g., IDMS, Total, … • Object-Relational Model • Relational Model – extends the relational model – the most widely used now – e.g., Postgres, Informix, DB2, Oracle, … – e.g., System R, Ingres, … • *Semi-structured Data* • Entity-Relationship Model – focus on data in XML format – a conceptual modelDBMS: Overview of DB Systems 15 Dr. Kriengkrai Porkaew
  16. 16. Data Models – Diagrams Hierarchical and Network customer account own name address number balance customer account name address number balance Network data-structure diagram customer account virtual account virtual customer name address number balance custlink acctlink Hierarchical tree-structure diagram dummy DBTG data-structure diagramDBMS: Overview of DB Systems 16 Dr. Kriengkrai Porkaew
  17. 17. Data Models – Diagrams Relational, ER, OO name address number balance customer own account customer owner account Entity-Relationship diagram # name # name # number address # number balance Relational schema diagram customer account name 1..* 0..* number address balance UML class diagram (OO Model)DBMS: Overview of DB Systems 17 Dr. Kriengkrai Porkaew
  18. 18. Database Languages • Data Definition Language (DDL) – to specify the database schema. – Database schemas are stored in the data dictionary. – The data dictionary contains metadata. – Metadata: data about data, e.g. schema. • Data Manipulation Language (DML) – to express database queries and updates (include insertion, deletion, and modification) – Procedural DMLs -and- Declarative DMLsDBMS: Overview of DB Systems 18 Dr. Kriengkrai Porkaew
  19. 19. DB Languages: Examples Relational Model (SQL): Hierarchical Model (DL/I): DDL: DML: create table customer ( get first customer name char(30), where customer.name:=“Henry”; address char(60)); DML: Network Model (DBTG): select address DDL: from customer set name is custlink where name likes “Robert”; owner is customer member is dummy; Object-Oriented Model (ODMG): DML: DDL: customer.name := “Newton”; class customer:public object { find any customer using name; string name; get customer; string address; print(customer.address); set<ref<account>> accounts; };DBMS: Overview of DB Systems 19 Dr. Kriengkrai Porkaew
  20. 20. Data Manipulation Languages • Procedural DMLs – require a user to specify what data are needed and how to get those data – e.g., relational algebra; (C, Pascal, Java, etc.) • Declarative DMLs (nonprocedural DMLs) – require a user to specify what data are needed without specifying how to get those data – e.g. relational tuple calculus, relational domain calculus, SQL (core), Quel, QBE, Datalog; (Prolog) • A Query Language – is a part of DML that involves only retrieval of information (without updates) – However, a query language often means DMLDBMS: Overview of DB Systems 20 Dr. Kriengkrai Porkaew
  21. 21. What are the components of DBMSs? • A database system – is partitioned into modules that deal with each of the responsibilities of the overall system. • The functional components of a database system can be broadly divided into – the Query Processor Component: to simplify and facilitate access to data (convenient and efficient) – the Storage Manager Component: to minimize the need to move data between disk and main memory – the Transaction Manager Component: to handle atomicity and concurrency of transactions and consistency and durability of the databasesDBMS: Overview of DB Systems 21 Dr. Kriengkrai Porkaew
  22. 22. Query Processor Component • Query Processor: – A program module that provides the interface between the database and the application programs/queries • Components include: – DDL interpreter • interprets DDL commands and records them in the data dictionary – DML compiler • translates DML commands into query evaluation plans – Query evaluation engine • executes queries according to the plansDBMS: Overview of DB Systems 22 Dr. Kriengkrai Porkaew
  23. 23. Storage Manager Component • A Storage Manager is – A program module that provides the interface between the low-level data stored in the database and the application programs/queries submitted to the system • Components include: – Authorization and integrity manager – File manager – Buffer manager • Structures maintained: – data files, data dictionary, indicesDBMS: Overview of DB Systems 23 Dr. Kriengkrai Porkaew
  24. 24. Transaction Manager Component • Transaction: – a collection of operations that performs as a single logical function in a database application. • Transaction Properties: ACID – A tomicity: either all operations succeed or all of them fail – C onsistency: the database is changed from one consistent state to another consistent state – I solation: no transaction interfere other transactions in the middle – D urability: operations of successful transactions must persist • Components include – Transaction Manager – Lock Manager – Recovery ManagerDBMS: Overview of DB Systems 24 Dr. Kriengkrai Porkaew
  25. 25. DB System Structure application queries schemas programs API module DML compiler DDL interpreter query processor and optimizer buffer transaction manager manager recovery concurrency control manager storage lock manager manager index data dictionary dataDBMS: Overview of DB Systems 25 Dr. Kriengkrai Porkaew
  26. 26. Who interact with DBMSs? • Database Administrators (DBAs) • Database Operators • Database Designers • DB Application Developers/Programmers • End Users – Sophisticated End Users – Naïve End Users • DB System Designers and Implementers • Database Tool DevelopersDBMS: Overview of DB Systems 26 Dr. Kriengkrai Porkaew
  27. 27. DB Administrators (DBAs) and DB Operators • DBAs are responsible for – Starting up and shutting down the databases – Loading, importing, exporting data to/from the databases – Granting of authorization for using resources – Monitoring the use of the resources – Backing up the databases periodically and restoring the databases as needed – Tuning the system performance – Considering software and hardware upgrades • DB Operators are responsible for – {Helping DBAs maintaining normal DB operations}DBMS: Overview of DB Systems 27 Dr. Kriengkrai Porkaew
  28. 28. DB Designers and DB Developers / Programmers • Database Designers are responsible for – Analyzing data requirements – Designing the database structures • View, logical, and physical structures – Creating the databases • DB Application Developers / Programmers – Analyzing functional requirements – Developing program specifications from the requirements – Implementing those application programsDBMS: Overview of DB Systems 28 Dr. Kriengkrai Porkaew
  29. 29. End Users • Sophisticated End Users – Writing ad hoc queries to answer their own needs – Running ad hoc reports for executives/managers • Naïve End Users – Using customized applications developed by developers/programmers • Data entry operators, … • Executives, managers, …DBMS: Overview of DB Systems 29 Dr. Kriengkrai Porkaew
  30. 30. Participants on the implementation side of the database systems • DB System Designers and Implementers – Designing the structures and the functions of each component of the DBMSs – Implementing database components • File organizations, index structures, query processing, transaction management, DB API, user interface, … • DB Tool Developers – Designing and implementing tools for databases • Database design tools, application development tools, performance tuning tools, database administration tools, …DBMS: Overview of DB Systems 30 Dr. Kriengkrai Porkaew
  31. 31. Very Important Participants • Leaders in DB Industry Leaders in DB Research • – Leading Universities – Oracle • Stanford U. • ORACLE, RDB • UC Berkeley {Ingres, Postgres} – IBM • U of MD - College Park • DB2, Informix • U of Wisconsin - Madison – Microsoft – Research Labs • SQL Server, Access, FoxPro • IBM {System R, SQL, …} • ODBC, ADO • Microsoft • Bell Lab – Sybase • Sybase – Conferences/Journals • SIGMOD/POD, VLDB, EDBT, ICDE, RIDE, TKDE, …DBMS: Overview of DB Systems 31 Dr. Kriengkrai Porkaew
  32. 32. DBMS Market Share Windows 1999 2000 2001 New Licenses Revenue 2.4 B 2.5 B Revenue in Billion USD ORACLE 40.4% 38.1% 34.0% IBM 15.2% 19.9% 20.7% 1999 2000 2001 Microsoft 35.2% 35.4% 39.9% Revenue 7.9 B 8.8 B 8.8 B ORACLE 31.4% 33.8% 32.0% Unix 2000 2001 IBM 29.9% 30.1% 34.6% Revenue 3.6 B 3.0 B Microsoft 13.1% 14.9% 16.3% ORACLE 66.2% 63.3% Sybase ? 3.2% 2.6% IBM 14.4% 24.7% Informix ? 3.0% – Informix 6.7% – Source: Gartner DataquestDBMS: Overview of DB Systems 32 Dr. Kriengkrai Porkaew
  33. 33. Some Database Related Products • Commercial Products – Relational: Access, DB2, DBASE, FoxPro, Informix, Interbase, ORACLE, Paradox, RDB, SQL Server, Sybase, ThinkDB, UniSQL, etc. – OO: Cachè, Exodus, Gemstone, Iris, Jasmine, O2, Objectivity, ObjectStore, ODE, ONTOS, Orion, Versant, etc. – Hierarchical: IMS • Free/Open Source Products – Ingres, mSQL, MySQL, Postgres, etc. • Database APIs – ODBC, JDBC, ADO, …DBMS: Overview of DB Systems 33 Dr. Kriengkrai Porkaew
  34. 34. Examples of DB System Applications • Accounting • Manufacturing • Airlines • Telecommunication • Banking • Tourism • Finance • Transportation • Hospitals • Sales • Human Resources • Universities • Inventory • … (you name it) …DBMS: Overview of DB Systems 34 Dr. Kriengkrai Porkaew
  35. 35. Trends of Database Products • Present and Future: A Complete System • Past and Present: to – multimedia/complex data management support large amount of data and concurrent users – advanced OLTP: workflow – application development tools – data management of well-structured data – data repository: warehouse, data mart – on-line transaction – data analysis tools: processing (OLTP) • Online Analytical Processing (OLAP) – “Scalability” • Data Mining – a well-rounded system • web-enable, network-enable, • XML-compliant, multi-modelDBMS: Overview of DB Systems 35 Dr. Kriengkrai Porkaew
  36. 36. DBMS Architectures • Based on the number of users: – Single-user Systems • Only one user (one session) uses the system at a time – Multi-user Systems • Multiple users use the system at the same time • Based on the locations of the databases and their users – Stand-alone DBMSs • One DBMS supports its user(s) on the same machine – Client-Server (Centralized) DBMSs • One database server serves multiple clients – Distributed DBMSs • Coordination of multiple DBMSsDBMS: Overview of DB Systems 36 Dr. Kriengkrai Porkaew
  37. 37. Distributed DB Systems • Distributed DBMSs – Homogeneous Database Systems • Multiple subsystems which are of the same architectures spread around multiple remote sites – E.g., A system of multiple ORACLE on multiple computers at multiple remote sites – Heterogeneous Database Systems • Multiple systems which are of different architectures – E.g., A system of one DB2 + one SQL Server – Federated Database Systems – Also known as Multidatabase Systems • A kind of Heterogeneous Database Systems where each DBMS of the whole system has their own autonomyDBMS: Overview of DB Systems 37 Dr. Kriengkrai Porkaew
  38. 38. Distributed DBMSs ORACLE ORACLE SQL Server Federated DBMS Homogeneous Heterogeneous ORACLE ORACLE DB2DBMS: Overview of DB Systems 38 Dr. Kriengkrai Porkaew
  39. 39. DB Application Architectures • Client-Server (C/S) – Client machine: the database users work – Server machine: the database system runs • C/S: Two-tier architecture: small systems – Client: the DB users and the DB application – Server: the DB system • C/S: Three-tier architecture: large systems, web – Client sends requests to the application server – Application Server runs the application as a server for the client and as a client of the database server – Database Server runs the DBMSDBMS: Overview of DB Systems 39 Dr. Kriengkrai Porkaew
  40. 40. Client/Server Architecture Two-Tier Database Layer Application Layer Architecture 1 Three-Tier 2 Architecture Presentation Database Layer 2 1 Layer 3 4 Business Logic LayerDBMS: Overview of DB Systems 40 Dr. Kriengkrai Porkaew
  41. 41. What architectures are they? • A DBMS on a mainframe with multiple users; one on each terminal? • A DBMS on a PC running a web server that accesses the DBMS to provide services to its users? • A system connecting DBMSs of multiple companies together? • A system with a java application running on a web browser that sends requests to the web server which accesses a database on another machine?DBMS: Overview of DB Systems 41 Dr. Kriengkrai Porkaew
  42. 42. Specialized/Advanced DBMSs • Active DB Systems • Multimedia DB Systems • Data Warehouses • Parallel DBMSs • Deductive DB Systems • Text DB Systems • Genome DB Systems • Temporal DB Systems • Geographic Information • Spatial DB Systems Systems • Spatio-temporal DB • Main Memory DB Systems Systems • XML DB Systems • Mobile DB SystemsDBMS: Overview of DB Systems 42 Dr. Kriengkrai Porkaew
  43. 43. Conclusion Questions and AnswersDBMS: Overview of DB Systems 43 Dr. Kriengkrai Porkaew