The document discusses CICS file handling concepts, focusing on VSAM file types and their associated control commands, including random and sequential access, as well as error processing. It explains how to read, write, update, and delete records from VSAM files and highlights the commands used for browsing records. Additionally, it touches on the integration of CICS with DB2 and IMS databases, emphasizing the program preparation and improved performance through virtual storage.

1. CICS - DATA ACCESS
DAY 2 - SESSION 4
Updated in Nov 2004

2. Session 4 : ObjectivesTo Understand
CICS File handling Concepts
VSAM file types supported
VSAM File control Commands
VSAM File Browse Commands
Exceptions in File Handling
CICS-Database access : DB2 & IMS/DB

3. CICS Data Management

4. CICS and Database
Overview
RCT

5. CICS – VSAM File Handling
Supports VSAM
◦ BDAM supported in earlier versions of CICS
Files to be defined to CICS as resources in the FCT
File Opening, Closing done by CICS
Provides interface for
◦ Random access
◦ Sequential access
◦ Read, Write, Update, Delete

6. File Access Methods - VSAM
VSAM is the primary data access method for CICS
VSAM file types supported
◦ Key Sequenced Data Set (KSDS)
◦ Entry Sequenced Data Set (ESDS)
◦ Relative Record Data Set (RRDS)

7. Entry Sequenced Data Set
(ESDS)
Records to be
entered into
the data set
VSAM ESDS

8. ESDS - Relative Byte
Address
100
BYTES
REC1
200
BYTES
REC2
300
BYTES
REC3
0 100 200
RBA of REC3
is 200

9. Key Sequenced Data Set
(KSDS)
60
40
Key Field
20 25 58 63
Records For
Insert

10. Relative Record Data Set (RRDS)
REC3
REC1 REC2
REC5
REC3
SLOT 1 SLOT 2 SLOT 3 SLOT 4 SLOT 5

11. Record identification (RIDFLD)
RECORD KEY
PARTIAL KEY
RELATIVE BYTE ADDRESS (RBA)
RELATIVE RECORD NUMBER (RRN)

12. VSAM File – Random Access
Random Access
READ
WRITE a new record
REWRITE a record previously ‘read for update’
DELETE
UNLOCK a record previously ‘read for update’

13. VSAM File – Sequential
AccessSequential Read (Browsing)
Start Browsing
Read Next
Read Previous
End Browsing
Reset Browsing conditions

14. VSAM - READ from File :
Syntax
EXEC CICS READ DATASET(file-name)
INTO (rec-area)
LENGTH(record_length)]
RIDFLD(key-value)
RBA | RRN]
GENERIC]
KEYLENGTH(key-length)]
[UPDATE]
[GTEQ | EQUAL]
END-EXEC.

15. VSAM - READ from FILE : Example
WORKING- STORAGE SECTION.
77 WS-REC-LEN PIC S9(4) COMP.
77 WS-FILE-NAME PIC X(8) VALUE ‘ACCTMSTR’
01 WS-FILE-REC
05 WS-REC-KEY PIC X(6).
05 WS-REC-DATA PIC X(34).
PROCEDURE DIVISION.
MOVE 40 TO WS-REC-LEN.
MOVE ‘ABC451’ TO WS-REC-KEY.
EXEC CICS READ DATASET(WS-FILE-NAME)
INTO (WS-FILE-REC)
RIDFLD(WS-REC-KEY)
LENGTH(WS-REC-LEN)
END-EXEC.

16. VSAM – Steps to Add New
Records
WRITE NEW
RECORD
SET UP DATA VALUES
FOR NEW RECORD
MOVE KEY VALUE
TO RID FIELD

17. VSAM – Write to File : Syntax
EXEC CICS WRITE
DATASET(file-name)
FROM(file-rec)
LENGTH(rec-length)
RIDFLD(rec-key)
[RBA | RRN]
END-EXEC.

18. VSAM - File Update : Syntax
EXEC CICS REWRITE
DATASET (file-name)
FROM (data-area)
[LENGTH (rec-len)
END EXEC.

19. VSAM – File UnlockTo release a record previously read for update
EXEC CICS UNLOCK
FILE / DATASET (name)
END-EXEC.

20. VSAM - Delete From File :
Syntax
EXEC CICS DELETE
DATASET (file-name)
RIDFLD(rec-key)
[KEY-LENGTH(key-length)]
[GENERIC[NUMREC(rec-number)]]
[RBA | RRN]
END-EXEC.

21. VSAM - BROWSE Operation
ESTABLISH START
POSITION
RETRIEVE
NEXT RECORD
PROCESS
RECORD?
TERMINATE
BROWSE
END OF
BROWSE?
PROCESS
CHANGE
POSITION
YES
YES
YES
NO
NO
NO

22. VSAM - BROWSE CommandsSTARTBR - Establish starting position within file
READNEXT - Retrieve records in ascending order
sequentially as set by STARTBR
READPREV - Retrieve Records in descending
(reverse) order as set by STARTBR
RESETBR - Restart Browse by re-positioning the
pointer
ENDBR - Terminate Browse

23. VSAM - BROWSE : Example
MOVE ‘VALUE’ TO KEY-REC
EXEC CICS STARTBR FILE(‘FILEA’)
RIDFLD(RECKEY) RESP(ERR-CODE)
END-EXEC.
IF ERR-CODE = DFHRESP(NORMAL)
PERFORM UNTIL ERR-CODE = DFHRESP(ENDFILE).
PERFORM 2000-REC-FROM-FILE
UNTIL 2000-REC-FROM-FIL-EXIT
EXEC CICS READNEXT FILE(‘FILEA’)
INTO(FILEREC) RIDFLD(RECKEY)
RESP(ERR-CODE)
END-EXEC
END-PERFORM
EXEC CICS ENDBR FILE(‘FILEA’) …. END-EXEC
ELSE
PERFORM 9000-HANDLE-ERROR …..
END-IF.

24. File Handling - Exceptional
Conditions
Processing Information
◦ NOTFND
◦ ENDFILE
◦ LENGERR
Application Program Error
◦ INVREQ
◦ FILENOTFOUND
◦ ILLOGIC
◦ DUPREC
External Conditions
◦ IOERR
◦ DISABLED
◦ NOTOPEN
◦ NOSPACE

25. File Handling - Program
Organization
WORKING STORAGE
RECORD LAYOUT DEFINITION
RECORD ID FIELD
LINKAGE SECTION
EIB
PROCEDURE DIVISION
IDENTIFY KEY OF THE RECORD TO BE READ
EXEC CICS READ FILE....

26. CICS - Database Access
Provides Interface to
◦Hierarchical Database - IMS/DB
◦Relational Database - DB2

27. DB2 Database Access from
CICS
Terminal Users
CICS subsystem
CICS subsystem
Terminal Control & BMS modules
CICS - DB2 Attachment Facility Modules
DB2 Sub system
Appl.
pgm1
Appl.
pgm2
Appl.
pgm3
Threads
Tables, Files
Stored on disk
Other CICS
Modules

28. CICS - DB2 Program Preparation
Compile
Object
Module
Link-Edit
Load
Module
Compiler
Listing
Translated
Source
Source
Program
Translator
Listing
Translate
Precompile
Listing
Pre-Compile
Application
Plan
DBRM
Bind

29. Files - Data Tables
New feature of storing VSAM files in virtual
storage
Improved performance
◦ User Maintained Table(UMT)
◦ CICS Maintained Table (CMT)
◦ Shared Data Tables
Transparent to application program

30. Session 4 : Summary
CICS File handling - use of FCT
VSAM file types Supported - Random Access & Sequential
Read
File control commands - READ, WRITE, REWRITE, DELETE
Browse commands – STARTBR, READNEXT, READPREV,
RESETBR, ENDBR
Exceptional Conditions in File Handling
CICS-DB2 program preparation; RCT entries