Troubleshooting › Tape Device Dual Allocation Problems

Tape Device Dual Allocation Problems

Dual allocation occurs when the same device is allocated on two different systems at the same time. GTAF prevents dual allocation in a multiple-system environment by communicating allocation information among systems and extending locking mechanism z/OS uses to serialize allocation. However, under certain conditions, a dual allocation can occur while GTAF is running.

Most dual allocations occur because devices are not properly placed under CA MIA management. Another common cause is the way other software products interact with z/OS and GTAF. If you cannot attribute the dual allocation at your site to one of these possible causes, then you should contact CA Technical Support for assistance.

Possible cause:

GTAF is not active.

Solution:

Use the FACILITIES parameter on the DISPLAY command to see whether GTAF is active. If GTAF is not active, then do the following:

• Place the MIMINIT GTAF=ON statement in the initialization member to start GTAF automatically during CA MIM initialization.
• Manage the device manually until the next time CA MIM is started.

Possible cause:

The device was never placed under CA MIA management.

Solution:

Use the DISPLAY GLOBALUNITS command or inspect the MIM2004 message issued at startup/resynch to see whether CA MIA is managing the device. If CA MIA is not managing the device, then do the following:

• Place the device under CA MIA management through the MIMUNITS member.
• Assign a global name to the device, if necessary.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

The device was recently defined to the system during the SYSGEN process or using HCD, but not placed under CA MIA management.

Solution:

Use the DISPLAY GLOBALUNITS command or inspect the MIM2004 message issued at startup/resynch to see whether CA MIA is managing the device. If CA MIA is not managing the device, then do the following:

• Place the device under CA MIA management through the MIMUNITS member.
• Assign a global name to the device, if necessary.
• Issue the command SETOPTION GTAF RESYNCH SAMEDEVS=NO and change this value in the MIMCMNDS member to SAMEDEVS=NO for the next restart of CA MIA.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

The local name of the device was misspelled in the MIMUNITS member. As a result, GTAF is not managing the desired device.

Solution:

Review the MIM2004 messages to see whether the local name of the device was misspelled. You also can use the GLOBALUNITS parameter on the DISPLAY command to obtain this information.

If the local device name is misspelled, then do the following:

• Correct the entry in the MIMUNITS member.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

The device was not placed under CA MIA management on all systems. This is due to one of the following:

• MIMINIT statements were directed to only some of the systems in the complex. As a result, CA MIA is not managing the device on all systems.
• Device entries in the MIMUNITS member were directed only to certain systems, but not to all systems in the complex. As a result, CA MIA is not managing the device on all systems.
• Separate device control members are being used for each system, and this device was not included in every member.

Solution:

Review the contents of the CA MIM initialization member, which contains the MIMINIT statements, and each MIMUNITS member in use to determine where the error has occurred.

If CA MIA is not managing the device on all systems, then do the following:

• Add MIMINIT statements in the initialization member or add device entries to the MIMUNITS member to place devices under CA MIA management on the remaining systems.
• Assign global device names, if necessary.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

Global names were not assigned to every device that needs one.

Solution:

When global names are not specifically assigned, GTAF uses the local name of a device as its global name. This can cause dual allocation if two different devices use the same local name on different systems (for example, local name 01A0 refers to one device on System A and a different device on System B). Dual allocation also can occur if the device is allocated under different names on different systems (for example, the same device is allocated under local name 02A0 on System A and 03A0 on System B).

Review the MIM2004 messages to determine where global device names are required.

If global names were not assigned as required, then do the following:

• Assign global device names through the MIMUNITS member.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

A global name was assigned to that device; however, the global name is identical to the local name of a different device.

Solution:

Use the GLOBALUNITS parameter on the DISPLAY command to see the global and local names of all devices CA MIA is managing.

If the global name for that device is not unique, then do the following:

• Assign a different global device name through the MIMUNITS member.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

The same global name was not assigned to that device on all systems.

Solution:

Review the MIM2004 messages to see where the error occurred.

If the global device name is different on different systems, then do the following:

• Assign the same global device name on all systems through the MIMUNITS member.
• Force CA MIA to resynchronize by issuing the RESYNCH command.

Possible cause:

Another software product is in use that is bypassing the z/OS allocation process.

GTAF does not control allocation. It simply communicates information about allocations that have occurred during the z/OS allocation process. When software bypasses the z/OS allocation process, GTAF is not aware of those device allocations. Therefore, GTAF cannot prevent dual allocation.

Solution:

Do not use the software while GTAF is active.

More information:

Resynchronization: RESYNCH Command