Managing IMS subsystem inactivity manually

Follow these manual steps to prevent inactive IMS subsystems from affecting the performance of your replication environment.

About this task

InfoSphere® Classic CDC for z/OS® provides manual and automated options to manage the effects of inactive subsystems on latency or message activity.

Ideally, use the CECZ0400W message as a trigger to generate new activity automatically. You can do this by running a prepared BMP or WIFI region that generates a sufficient number of records to flush the buffers.

You can easily manage subsystem inactivity if your site can tolerate latency:

  • Wait for new activity on inactive subsystems to flush the buffers naturally and permit ordering operations to continue.
  • Set a higher value for the INACTTHRESHOLD parameter in the IMS log reader service (IMSL) to reduce message activity on the system console.

    If you do not expect update activity on inactive subsystems for an extended period of time, increasing this value reduces the frequency of the CECZ0400W message.

Use the following steps to manage inactive subsystems manually in response to the CECZ0400W message:

Procedure

  • If you do not expect workload on the identified subsystem, shut it down.

    The source server removes this subsystem from ordering decisions.

  • Issue the IMS command /CHECKPOINT for the identified subsystem.

    This is a temporary measure that flushes the buffers and writes their log records to the online data sets (OLDS). Ordering operations can continue to merge changes from all participating subsystems until one of the following events occurs:

    • The period of time elapses that you specified in the INACTTHRESHOLD parameter
    • A subsystem becomes inactive