COMMAREA

What is a COMMAREA

• COMMAREA is short for Communication Area.
• It is a data area used to pass data from one CICS program to another.
• You name it on the LINK, XCTL or RETURN command with the COMMAREA option.
• The program that receives it must define a field named DFHCOMMAREA in its Linkage Section.
• CICS puts the length of the COMMAREA in the EIBCALEN field (S9(4) COMP).
• Always check EIBCALEN before using DFHCOMMAREA.

How a program receives a COMMAREA

• Define 01 DFHCOMMAREA in the Linkage Section with the same layout as the sender uses.
• On the very first execution of a pseudo-conversational program, EIBCALEN is 0.
• When EIBCALEN is 0, DFHCOMMAREA contains LOW-VALUES. Move your working area there after the first screen display.
• If you forget the EIBCALEN check, your program may use garbage data on the first run.
• Example of receiving and sending a COMMAREA:-
  LINKAGE SECTION. 01 DFHCOMMAREA PIC X(200). PROCEDURE DIVISION. 0000-MAIN-PARA. IF EIBCALEN = 0 MOVE LOW-VALUES TO WS-COMM-AREA ELSE MOVE DFHCOMMAREA TO WS-COMM-AREA END-IF. . . EXEC CICS LINK PROGRAM('PROG2') COMMAREA(WS-COMM-AREA) LENGTH(200) END-EXEC.

How a program sends a COMMAREA

• Use the COMMAREA(data-name) option on LINK, XCTL or RETURN.
• Always give the LENGTH option with the number of bytes being passed.
• Both the sending and receiving programs must agree on the layout.
• The LENGTH you pass must not be larger than the DFHCOMMAREA defined by the receiver.