Passing Data Between Programs

Ways to pass data between CICS programs

• COMMAREA: one flat data area passed on LINK, XCTL or RETURN. Simple, but both programs must agree on the layout.
• CHANNEL with CONTAINERs: many named data items passed on LINK, XCTL, START or RETURN. Flexible and easy to extend.
• CICS storage areas: CWA, TWA and TCTUA. Shared storage reached with the ADDRESS command.
• Temporary storage queues: one program writes, another reads. Good for larger data.
• Files and DB2 tables: pass a key in the COMMAREA and let each program read the record itself.

COMMAREA vs CHANNEL - which to use

• Use COMMAREA for small, fixed data where both programs are written together.
• Use CHANNEL when the data has many parts, or when different programs need different parts.
• Use CHANNEL when the called program must send changed data back to the caller.
• Adding a container never breaks existing programs. Changing a COMMAREA layout can break them.
• For new development, CHANNEL is the recommended approach.

Sharing data with CWA, TWA and TCTUA

• CWA is the Common Work Area. It is shared by all tasks in the CICS region.
• TWA is the Transaction Work Area. It belongs to the current task.
• TCTUA is the Terminal Control Table User Area. It belongs to the terminal.
• Use the ADDRESS command to get addressability to these areas through the Linkage Section.
• Example of using the CWA:-
  LINKAGE SECTION. * 01 DFHCOMMAREA PIC X. * 01 COMMON-WORK-AREA. * 05 CWA-CURRENT-DATE PIC X(8). 05 CWA-COMPANY-NAME PIC X(30). * PROCEDURE DIVISION. * 0000-PROCESS-CUSTOMER-INQUIRY. * EXEC CICS ADDRESS CWA(ADDRESS OF COMMON-WORK-AREA) END-EXEC. MOVE CWA-COMPANY-NAME TO COMPO.