Advanced Topics › Tape Device Allocation and Allocation Recovery Considerations › z/OS Device Allocation Recovery with CA MIA

z/OS Device Allocation Recovery with CA MIA

The CA MIA facilities play different roles in the allocation recovery process. GTAF propagates the effect of allocation recovery to all systems, while TPCF influences device selection and automatically responds to z/OS allocation recovery messages.

z/OS suspends SWAP processing and certain device group requests while an allocation recovery message is outstanding, because the job in allocation recovery holds the device group locks until the recovery message is replied to. Because GTAF propagates this effect to other systems, you must respond promptly to all allocation recovery messages on all systems, or tell TPCF to reply automatically.

TPCF uses the values you have specified on the SETOPTION command to determine how to respond to z/OS allocation recovery messages. You should also realize that CA MIA facilities only affect allocation recovery when a managed device is in the EDL for a job.

To influence device selection, TPCF intercepts the z/OS offline device list and removes devices from it according to your preferencing criteria. TPCF obtains this criteria from the elimination logic you have defined in the TPCRECXT exit routine and from device status changes you have made through the VARY command.

Note: Either TPCF or the exit may remove the DEVICE NAME option on the z/OS IEF238D message when TPCF makes this option unavailable. For example, if TPCF removes all devices from the offline device list, then the DEVICE NAME option on message IEF238D is removed.

The following steps give you an overview of the role of CA MIA in the allocation recovery processing:

1. z/OS creates the offline device list and a list of wait-eligible devices from the EDL of that job.
2. z/OS passes the allocation recovery information to any recovery exits loaded at the IEF_SPEC_WAIT or IEF_ALL_OFFLN exit points. TPCF acts as an exit at both exit points. TPCF examines the offline device list and removes these devices from the list:
   • Devices that are overgenned
   • Devices reserved for a different job
   • Devices removed by the elimination logic in the TPCEDLXT exit or devices removed by the TPCRECXT exit

   In the exit parameter list, z/OS lists the possible ways to get this job out of allocation recovery. TPCF examines these options, which are usually DEVICE NAME, WAIT, or CANCEL.

   If WAIT is not an option and this step removes all devices on the offline device list, then TPCF tells z/OS to cancel the job. TPCF skips all remaining steps in this diagram.

   TPCF responds to the allocation recovery according to the value you specified on the IEF238D operand on the SETOPTION AUTOREPLY command, or to the value entered for the optional TPCRECXT exit routine, which would override SETOPTION values:

   • If you specified CANCEL, then TPCF removes not-available and externally dedicated devices from the offline device list. TPCF then takes one of these actions:
     • When there are no devices left on the offline device list, TPCF replies CANCEL. This tells z/OS to cancel the job, and TPCF skips all remaining steps in this diagram.
     • When at least one device remains, TPCF asks the operator to reply.
   • If you specified WAIT, then TPCF does one of the following:
     • When WAIT is an option on the z/OS message, TPCF replies WAIT so that the job waits for an online device to be deallocated. TPCF then goes directly to Step 4.
     • When WAIT is not an option on the z/OS message, TPCF removes unavailable and externally dedicated devices from the offline device list unless doing so would remove all devices. If doing so would remove all devices, then TPCF lists externally dedicated or not available devices based on the SETOPTION TPCF AUTOREPLY=(NOWAIT=(EXTDEDDISP=,NOTAVLDISP=)) settings. If there are devices listed in the offline device list, then TPCF asks the operator to reply. If there are no offline devices, then TPCF replies CANCEL.
   • If you specified COND, then TPCF does one of the following:
     • When WAIT is an option on the z/OS message and TPCF removes all devices from the offline device list, TPCF replies WAIT. This makes the job wait for an online device to be deallocated. TPCF then goes directly to Step 4. If there are offline devices, then TPCF asks the operator to reply.
     • When WAIT is not an option on the z/OS message, or if TPCF does not remove all devices from the offline device list, TPCF asks the operator to reply. Externally dedicated or not available devices may be listed in the offline device list if there are no other offline devices based on the SETOPTION TPCF AUTOREPLY=(NOWAIT=(EXTDEDDISP=,NOTAVLDISP=)) settings.
   • If you specified MANUAL, then TPCF removes unavailable and externally dedicated devices from the offline device list (if possible). Externally dedicated or not available devices may be listed in the offline device list if there are no other offline devices based on the SETOPTION TPCF AUTOREPLY=(NOWAIT=(EXTDEDDISP=,NOTAVLDISP=)) settings. TPCF then asks the operator to reply.
3. TPCF issues message MIM2060 whenever it needs to ask the operator to reply. Message MIM2060 shows you the options you have in responding to the allocation recovery after TPCF has removed any additional devices from the offline candidate list. If there are offline devices to choose from, then TPCF also issues message MIM2042 to show you the names of these devices.
4. If TPCF replied WAIT for the allocation recovery, then TPCF also replies with a IEF443D option according to the value you specified on the IEF433D operand on the SETOPTION AUTOREPLY command, or to the values entered for the optional TPCRECXT exit routine, which would override SETOPTION values:
   • If you specified HOLD, then TPCF replies HOLD. This tells z/OS to hold the locks to all of the device groups on the EDL of this job. As a result, other jobs needing these device groups must wait until the current job allocates a device.
   • If you specified NOHOLD, then TPCF replies NOHOLD. This tells z/OS to release the device group locks this job is holding so that other jobs can use this device group while the current job is waiting for a device.
   • If you specified MANUAL, then TPCF asks the operator for assistance.
5. When the TPCF exit point has processed the allocation recovery, the job continues through the z/OS allocation recovery process.

More information:

Verify Whether Devices are Defined to CA MIA