CQS warm start

During a warm start, CQS reads the log records from the last system checkpoint, restores the environment for committed data objects, and backs out uncommitted data objects to prepare CQS to regain synchronization with the client and resume processing. Normally, a CQS warm start is automatic and you do not need to take any action.

When CQS warm starts, it reads the checkpoint data set to find the log token representing the last system checkpoint. When CQS finds this log token, it initiates a warm start. If CQS fails to find this log token in the checkpoint data set, it reads the log token from the structure. If CQS finds the log token, CQS issues WTOR CQS0031A to allow you to confirm the use of this token. At this point, you can do one of the following:

  • Confirm the log token
  • Cold start CQS
  • Cancel CQS
  • Specify a new log token

If you specify a new log token and CQS fails to find this log token, CQS issues WTOR CQS0032A. At this point, you can take one of the following actions:

  • Cold start CQS
  • Cancel CQS
  • Specify a new log token

Sometimes, CQS purges log records that are required for restart. CQS purges log records in the following situations:

  • During a structure checkpoint
  • When the log becomes full and no more data sets are available for logging
Important: CQS might not have any log records if it is only managing resource structures.
Recommendation: If a CQS does not accept a log token during CQS restart, cold start the CQS. In cases where multiple CQSs are running, it is possible that log records for a CQS that previously failed and was not restarted are purged while another CQS performs a structure checkpoint.