AR/CTL checkpoint/restart services

Checkpoint/restart services provide (or enhance) an environment that allows an application program job step to be restarted from an application checkpoint after a failure.

These services perform the following processing:

Restart processing

Restart processing includes program restart at the last checkpoint, automatic repositioning of data structures that use AR/CTL data services, and restoration of working storage areas. AR/CTL provides several methods for an application program to obtain restart processing; the Automatic Restart options require no program changes.

Checkpoint processing

Checkpoint processing includes saving application program working storage areas; saving information needed to reestablish program position within the data sets that use AR/CTL data services; and signaling all database management systems (DBMSs), such as DB2 and IMS, to perform commit processing. AR/CTL provides several methods for an application program to obtain checkpoint processing; the Automatic Checkpoints options require no program changes.

Automated management of checkpoint/restart data sets

AR/CTL creates, dynamically allocates, and deletes required checkpoint/restart data sets at appropriate points during application program execution.

Automated determination of checkpoint/restart requirements

AR/CTL monitors program execution status, selects the correct checkpoint for restart, and provides checkpoint information to participants in the application execution environment.

Checkpoint pacing by shift

Checkpoint pacing includes monitoring the threshold (maximum) interval allowed without a checkpoint, controlling (pacing) the minimum interval between checkpoints, and bypassing checkpoints that do not meet the defined pacing requirements.

Application reattach options

AR/CTL can invoke dynamic backout in certain abend conditions (such as deadlock and rollback) and can reattach the application program task instead of terminating the task.