CQS structure recovery for restarting
A structure might need to be recovered if the structure is empty or if it contains only Common Queue Server (CQS) control information. Data from the last structure checkpoint and the z/OS® log stream are used to recover a structure.
The structure is first repopulated with data objects from the structure recovery data sets. CQS then reads the log, starting at the time of the structure checkpoint, and updates the structure with changes that occurred after the structure checkpoint.
If
the primary structure is empty and neither SRDS contains valid structure
checkpoint data, CQS determines whether it can use just the CQS log
for recovery. If the first log record in the log stream is the Beginning
of Log
record, the log stream contains all the log records required
for recovery, and CQS can use the log records to complete the structure
recovery.
If CQS finds that a previous structure rebuild did not complete successfully, it initiates another rebuild.
If the primary structure contains only CQS control information and the first CQS that connected to the structure (the one that allocated the structure) cannot determine whether a rebuild is needed, CQS initiates a rebuild if either SRDS is valid or if all the log records are available.
If neither SRDS is valid and the log records have been deleted by a previous structure checkpoint, CQS cannot rebuild the structure. When this happens and a rebuild is necessary, CQS issues write-to-operator-with-reply (WTOR) CQS0034A message asking what you want to do. You can cold start the structure or cancel this CQS.