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COBOL Considerations

COBOL Considerations. Identification Division. No differences Environment Division MUST be EMPTY in CICS Program! No SELECT statements allowed! Data Division No FILE SECTION – (No SELECTS). COBOL Considerations (More). Data Division WORKING-STORAGE SECTION.

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COBOL Considerations

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  1. COBOL Considerations • Identification Division. • No differences • Environment Division • MUST be EMPTY in CICS Program! • No SELECT statements allowed! • Data Division • No FILE SECTION – (No SELECTS) CICS-Prg

  2. COBOL Considerations (More) • Data Division • WORKING-STORAGE SECTION. • Switches, Flags, Variables, Records, etc. • You get ‘fresh’ copy each time program loaded! • LINKAGE SECTION (New Item!!) • DFHCOMMAREA defined or CICS will! • Used to receive data from CICS. • CICS also inserts EIB Block definition CICS-Prg

  3. COBOL Considerations (More) • Procedure Division • Uses most COBOL statements • Also uses CICS Commands like: • SEND MAP • RECEIVE MAP • READ DATASET • WRITE DATASET • RETURN • XCTL CICS-Prg

  4. Where are WE? • Program must be able to determine! • Always starts at beginning of Program • Starts with initialized Working-Storage • Can use several methods: • EIBCALEN (First time program loaded) • COMMAREA (Tran-ID, EIBAID) • Hidden Data on Screen CICS-Prg

  5. Where are We? (More) • Beginning of Program must determine! • Can use series of ‘IF’ statements • Can be nested (or not if careful!) • Usually each path ends with RETURN • Can use EVALUATE statement (Newer!) • EVALUATE TRUE most common (New Dev) • General WHEN OTHER for errors CICS-Prg

  6. Sample CICS COBOL Program • WORKING-STORAGE SECTION. • Switches, Flags, and Misc Variables • COMMUNICATION-AREA (Your copy!) • RESPONSE-CODE PIC S9(08) COMP. • RECORD Descriptions • COPY Library for MAP • Other COPY Members as needed CICS-Prg

  7. Sample CICS COBOL Program • LINKAGE SECTION. • DFHCOMMAREA PIC X(nnn). • If you don’t code it, CICS Will! • The commarea (if any) placed here! • EIBCALEN gives length of commarea • 0 (ZERO) means there is NO commarea CICS-Prg

  8. Sample CICS COBOL Program • PROCEDURE DIVISION (Where are we?) IF first-time SEND Initial-Map ELSE IF <ENTER> Process Screen ELSE Process Function-Key END-IF END-IF SEND MAP CICS-Prg

  9. Sample CICS COBOL Program • PROCEDURE DIVISION EVALUATE TRUE WHEN EIBCALEN = 0 Send Initial MAP WHEN EIBAID = DFHENTER Process Screen Data WHEN EIBAID = DFHPF3 or DFHPF12 Exit Program WHEN OTHER Invalid key END-EVALUATE CICS-Prg

  10. Basic CICS Commands • General Structure: EXEC CICS CICS COMMAND OPTION(value) … (Parameters as needed) END-EXEC CICS-Prg

  11. Basic CICS Commands EXEC CICS SEND MAP(name) [ MAPSET(name) ] [ FROM(data-area) ] [ MAPONLY | DATAONLY ] [ ERASE | ERASEUP ] [ CURSOR [ (value) ] ] END-EXEC CICS-Prg

  12. Basic CICS Commands EXEC CICS RECEIVE MAP(map-name) [ MAPSET(mapset-name) ] INTO(data-area) END-EXEC CICS-Prg

  13. Basic CICS Commands EXEC CICS RETURN [ TRANSID(name) ] [ COMMAREA(data-area) ] [ LENGTH(data-value) ] END-EXEC Length – PIC S9(4) COMP or Literal CICS-Prg

  14. Program Control Commands EXEC CICS XCTL PROGRAM(name) [ COMMAREA(data-area) ] [ LENGTH(data-value) ] END-EXEC NOTE: Program name must be in PPT. Works like COBOL ‘GO TO’ statement. CICS-Prg

  15. Program Control Commands EXEC CICS LINK PROGRAM(name) [ COMMAREA(data-area) ] [ LENGTH(data-value) ] END-EXEC NOTE: Program name must be in PPT. Works like COBOL ‘PERFORM’ statement. CICS-Prg

  16. Basic CICS Commands EXEC CICS READ DATASET(filename) INTO(data-area) RIDFLD(data-area) [ RRN | RBA ] [ UPDATE ] END-EXEC CICS-Prg

  17. More CICS Commands EXEC CICS WRITE DATASET(filename) FROM(data-area) RIDFLD(data-area) [ RRN | RBA ] END-EXEC CICS-Prg

  18. More CICS Commands EXEC CICS REWRITE DATASET(filename) FROM(data-area) END-EXEC NOTES: Record MUST be READ with UPDATE! data-area - NOT have to match Read CICS-Prg

  19. More CICS Commands EXEC CICS DELETE DATASET(filename) [ RIDFLD(data-area) ] [ RRN | RBA ] END-EXEC NOTE: If no RIDFLD last READ is Deleted CICS-Prg

  20. Basic CICS Commands EXEC CICS ABEND [ ABCODE(name) ] END-EXEC (ABCODE used to identify storage dump - Usually omitted!) CICS-Prg

  21. CICS Program Design • Event-driven design • Structure Chart - Consider All Functions • Identify Events and Context • Any action that starts program • List All (Valid) Possible User Actions • Design Appropriate Response • Processing required for an event • Managing user interaction CICS-Prg

  22. CICS Program Design • COMMAREA usually stores ‘context’ • Get Key • Add Customer • Change Customer • Delete Customer • Response to same key can be different depending on ‘context’ (ENTER key) CICS-Prg

  23. CICS Program Design • Event/Response Chart • Helps with design or Program • Serves as Documentation of Program • Sometimes replaced with ‘Structure Chart’ • Structure Chart ‘Evolves’ into Design • Start with Major Functions • Add Detail as Needed • Assign Paragraph Numbering (If Used) CICS-Prg

  24. More CICS Commands EXEC CICS UNLOCK DATASET(filename) END-EXEC NOTE: If READ/UPDATE command is used and you determine that record does not need to be updated. Usually not needed as record is unlocked when the task is terminated. CICS-Prg

  25. Exception Conditions • Most Common Exceptions: • DISABLED Dataset disabled • DUPREC Record already exists • FILENOTFND Dataset not in FCT • INVREQ Invalid request • IOERR File I/O error • NOTAUTH User not authorized • NOTFND Record not in file CICS-Prg

  26. Checking for Exceptions • ALL CICS Commands allow RESP Parm • 01 RESP-CODE PIC S9(8) COMP. IF RESP-CODE = DFHRESP(NORMAL) MOVE ‘Y’ TO OK-COMMAND ELSE IF RESP-CODE = DFHRESP(NOTFND) MOVE ‘N’ TO REC-NOT-FOUND ELSE PERFORM DISPLAY-MISC-ERROR END-IF END-IF CICS-Prg

  27. Preventing File Corruption • PREVENT • Add ‘busy’ flag in record (Special Maint) • All programs MUST follow procedure • Extra I/O required (to Set/Reset flag) • DETECT • Save copy and compare before updating • OR – Add Maint-Timestamp and check it • Notify User to get latest version of data CICS-Prg

  28. Avoiding Deadlock • Sometimes called ‘Deadly Embrace’ • Happens when records from multiple files must be updated as a unit • Withdraw from Savings – Deposit to Check • Crash after withdraw? Where’s money? • Must both be done or neither! (Atomic) CICS-Prg

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