This option applies only if the Automatic Restart option is set to Y.

You can have AR/CTL issue checkpoint requests automatically for the application program, based on activity against a trigger. The program cannot issue an explicit request for checkpoint services. With the automatic checkpoint options, you may be able to avoid making program changes to implement AR/CTL checkpoint services in that program.

AR/CTL initiates automatic checkpoints in response to the specified count of I/O or fetch requests against the trigger, which can be a QSAM or VSAM file, a DB2 cursor, or an IMS PCB. Alternately, AR/CTL initiates automatic checkpoints when a user-defined unit-of-work boundary is crossed on a QSAM trigger file. Whether a checkpoint request completes depends on the checkpoint pacing options in effect.

You cannot change the value of this option between abend and restart of the application program.

If you set this option to Y, you must set related options as explained in Using the Automatic Restart Options panel. For more information about checkpoint services, see Using.

For an application program that issues explicit requests for checkpoint services (including DB2 commits), you must set this option to N. If an application program issues explicit requests and you have set the option to Y, the program terminates abnormally when AR/CTL detects that checkpoints have been initiated from different sources.

When this option is set to Y for an IMS program, AR/CTL saves the entire working storage area of the application program at each checkpoint performed. For programs (especially in a DLI batch environment) that have large working storage areas, consider the impact of writing the checkpoint records to the IMS logs and take appropriate action to prevent problems.

For IMS programs that use automatic checkpoints, parentage (obtained with the *P command code in the SSA) is not set at restart. If the program depends on the database structure, use a PCB instead of a file as a trigger for automatic checkpoints.

Note

When a checkpoint call is issued, database position is lost. AR/CTL must reestablish the database position of the automatic checkpoint trigger by issuing a GU call or through some other method. Database position cannot be reestablished in the middle of non-unique keys or non-keyed segments. Therefore, results are unpredictable if any of the sensitive segments of the IMS PCB being used to trigger automatic checkpoints are non-keyed or have non-unique keys.

For an IMS program to use automatic checkpoints, the PSB must be generated with COMPAT=Y.

The Automatic Checkpoints option is not available for IMS compatible programs.