CA MIA intercepts requests to VARY a CA MIA managed device ONLINE or OFFLINE. If a VARY request originated from an intercepted z/OS VARY command, then an acknowledgment is directed back to the origin console. The VARY device request is then sent to the CA MIA address space for processing. Multiple requests for the same device are maintained in first in, first out order so that the proper online and offline processing sequence is maintained.
CA MIA can optionally delete redundant VARY commands when a sequence of duplicate VARY commands is intercepted. By default, this feature is disabled. The SETOPTION VARYDEDUP command is used to enable the deletion of duplicate VARY commands.
CA MIA attaches up to eight concurrent VARY service subtasks to perform VARY processing. Additional incoming VARY requests remain queued by CA MIA until one of the eight VARY subtasks completes and is detached.
When CA MIA intercepts a VARY device request, CA MIA determines if there are VARY requests for the device already being processed. If there are no active VARY requests for the device, CA MIA attaches a service subtask to process the request. If there are active VARY requests for the device, CA MIA queues the incoming request to the existing subtask processing VARY requests for the device. A given subtask is only responsible for servicing VARY requests for a single device.
When a VARY service subtask is excessively delayed in obtaining the respective device group lock, the service task times out. Timed out VARY requests are re-queued. Timeout processing ensures that a VARY request that cannot obtain device group locks will not excessively delay other requests.
CA MIA VARY Device Service subtasks call the IBM IEEVARYD service routine to process VARY device requests. The results of VARY device requests are logged in SYSLOG by the IEEVARYD service routine regardless of the command origin.
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