1. COBOL Considerations Identification Division. Environment Division
No differences
Environment Division
MUST be EMPTY in CICS Program!
No SELECT statements allowed!
Data Division
No FILE SECTION – (No SELECTS)
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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
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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
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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
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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
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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
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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
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8. Sample CICS COBOL Program
PROCEDURE DIVISION (Where are we?)
IF first-time
SEND Initial-Map
ELSE
IF <ENTER>
Process Screen
Process Function-Key
END-IF
SEND MAP
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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
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10. Basic CICS Commands General Structure: EXEC CICS CICS COMMAND
OPTION(value) …
(Parameters as needed)
END-EXEC
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11. Basic CICS Commands EXEC CICS SEND MAP(name) [ MAPSET(name) ]
[ FROM(data-area) ]
[ MAPONLY | DATAONLY ]
[ ERASE | ERASEUP ]
[ CURSOR [ (value) ] ]
END-EXEC
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12. Basic CICS Commands EXEC CICS RECEIVE MAP(map-name)
[ MAPSET(mapset-name) ]
INTO(data-area)
END-EXEC
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13. Basic CICS Commands EXEC CICS RETURN [ TRANSID(name) ]
[ COMMAREA(data-area) ]
[ LENGTH(data-value) ]
END-EXEC
Length – PIC S9(4) COMP or Literal
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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.
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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.
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16. Basic CICS Commands EXEC CICS READ DATASET(filename) INTO(data-area)
RIDFLD(data-area)
[ RRN | RBA ]
[ UPDATE ]
END-EXEC
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17. More CICS Commands EXEC CICS WRITE DATASET(filename) FROM(data-area)
RIDFLD(data-area)
[ RRN | RBA ]
END-EXEC
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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
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19. More CICS Commands EXEC CICS DELETE DATASET(filename)
[ RIDFLD(data-area) ]
[ RRN | RBA ]
END-EXEC
NOTE: If no RIDFLD last READ is Deleted
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20. Basic CICS Commands EXEC CICS ABEND [ ABCODE(name) ] END-EXEC
(ABCODE used to identify storage dump -
Usually omitted!)
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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
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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)
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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)
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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.
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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
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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
PERFORM DISPLAY-MISC-ERROR
END-IF
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27. Preventing File Corruption
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
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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)
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