z/OS serializes allocation using device group locks. When a job goes into allocation recovery, it generates message IEF238D, which lists the options available in recovery for this current allocation request.
A subsequent WTOR, message IEF433D, is issued requesting operator intervention to determine whether the subset of the device group locks requested by this job should be held until the remainder of the locks become available. The operator can reply HOLD or NOHOLD to this message. While either of these WTORs is outstanding, allocation of devices represented by these device group locks on the local system stops. That is, the job in allocation recovery holds device group locks and other jobs wanting the locks must wait until the WTORs for the job in recovery are replied to.
When CA MIA is started, it extends the local z/OS serialization to all systems in the MIMplex. Allocation stops on all systems for all jobs requesting even a subset of the device group locks held by the task for which the allocation recovery prompt was issued.
As soon as the WTOR has been responded to, allocation resumes on all systems. For this reason, we recommend that outstanding Allocation Recovery prompt replies should be automated. The AUTOREPLY function of TPCF performs this function, and can virtually eliminate the need for manual operator intervention in allocation recovery.
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