Suppressing excessive checkpoints1

The Checkpoint Pacing feature is a feature of Application Director that controls the frequency of checkpoints in IMS BMP, IFP, DLI, and DBB jobs based upon minimum criteria specifications that are issued by the application program.

The Checkpoint Pacing feature of Application Director does not take checkpoints on behalf of the application program. The application program is still in control of its own processing and responsible for database repositioning after the checkpoint.

You can control the checkpoint frequency by eliminating excessive checkpoints based upon:

• Minimum time interval since last checkpoint
• Minimum number of DL/I Calls issued since last checkpoint
• Minimum number of DL/I database updates since last checkpoint

The application program can be notified of these suppressed checkpoints using any or all of these codes:

• PCB status code
• AIB return code
• AIB reason code

Application Director ANDs the values together. The application must meet all the minimum values or the checkpoint is suppressed.

When checkpoints are suppressed, a special PCB status code can be returned to the application program. This status code can be used by the application program to eliminate any unnecessary repositioning calls. Special return and reason codes can be set in the Application Interface Block for AIBTDLI callers.

For example, if you specify:

• 120 seconds for the Minimum Time Interval customizable parameter
• 100 for the Minimum DL/I Calls customizable parameter
• 6 for the Minimum DL/I Updates customizable parameter

For these values, a checkpoint is suppressed unless all of these conditions occur.

• 120 seconds have passed since the last checkpoint.
• 100 DL/I calls have occurred since the last checkpoint.
• 6 DL/I updates have occurred since the last checkpoint.

To use the Checkpoint Pacing feature, you must enable Application Director in the IMS BMP, IFP, DLI, and DBB jobs. Once you have enabled Application Director and specified the values for Checkpoint Pacing, the values are used whenever the application program is running.

• Methods-for-suppressing-excessive-checkpoints There is more than one method that you can use to suppress excessive checkpoints.
• Specify-values-for-checkpoint-pacing Using any of the 3 methods, you specify the values you want BMC Application Director for IMS to use for checkpoint pacing.
• Suppressing-excessive-checkpoints-using-customizable-parameters When you customized BMC Application Director for IMS, you specified the values for checkpoint pacing. You can verify or change the values using option G (Globals) on the BMC Application Director Management Interface.
• Suppressing-excessive-checkpoints-using-the-interface Use the following procedure to suppress excessive checkpoints using the Database Director Management Interface.
• Suppress-excessive-checkpoints-using-the-SET-CHECKPOINTPACING-command If you want to override the values specified for the customizable parameters or in the interface for checkpoint pacing, you can use the SET CHECKPOINTPACING command and keywords.