Coding an I/O area

In the working storage of the application program, identify the I/O area to use for the common call. AR/CTL uses this area to communicate a restart ID to the program, and the program can use this area to communicate a checkpoint ID to AR/CTL.

The application program must initialize the I/O area to blanks before issuing the restart call.

In response to the restart request, AR/CTL inserts the restart ID into the I/O area if the program is restarting. The program should look at this area and take appropriate action for a restart, if necessary. AR/CTL leaves this area as blanks (X'40') if the application program is starting normally.

The program can insert a checkpoint ID into this area before issuing a checkpoint request, or the program can leave this area blank. If this area is blank, AR/CTL automatically generates a checkpoint ID for the program:

For IMS programs, AR/CTL returns the generated checkpoint ID or message from IMS in this area.
For IMS compatible, DB2 only, VSAM-only, and DB2/VSAM programs, AR/CTL returns the generated checkpoint ID in this area.

The checkpoint identifier will be incremented automatically for all AR/CTL common CHKP calls if the checkpoint identifier in the first AR/CTL common CHKP call contains all blanks (X'40').

The following example shows the restart ID area as coded in COBOL:

IDENTIFICATION DIVISION.
...
DATA DIVISION.
WORKING-STORAGE SECTION.
01   XRSTID-AREA.
     02 XRSTID PICTURE X(12).

Coding an I/O area

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