Advanced Topics › z/VM Considerations › Guests Attached by MULTIuser Option

Guests Attached by MULTIuser Option

You must specify the GTAINIT ASSIGN=NOASSIGN parameter if any device managed by CA MIA is attached to the guest using the MULTIuser option.

Devices attached to guests using the MULTIuser option do not currently support MULTISYSTEM ASSIGN. Control Program (CP) has been enhanced to support only ASSIGN and UNASSIGN processing types for MULTIuser attached devices. If a MULTIuser attached device receives MULTISYSTEM ASSIGN information, then an I/O error is returned.

Example:

If a z/OS guest of z/VM sends a MULTISYSTEM ASSIGN command to a MULTIuser attached device, then the guest receives an I/O error for the device from the z/VM host. If the guest specifies the GTAINIT ASSIGN=MULTISYSTEM parameter, then CA MIA changes specifications for managed devices from ASSIGN to MULTISYSTEM ASSIGN.

Devices are assigned at VARY ONLINE time; therefore, when a VARY ONLINE command is issued, any MULTIuser attached device managed by CA MIA receives an I/O error from the z/VM host, and the device is not brought online. Similarly, if the GTAINIT ASSIGN=ASIS parameter is specified and a VARY ONLINE,SHR command is issued for a MULTIuser attached, managed device (appending the SHR option requests MULTISYSTEM ASSIGN), then an I/O error is received from the z/VM host, and the device is not brought online.

To eliminate I/O errors, specify the GTAINIT ASSIGN=NOASSIGN parameter.

Note: MULTISYSTEM ASSIGNS (VARY ONLINE,SHR) that are run against non-managed devices or against devices on guests where CA MIA is not running receive I/O errors if the devices are attached to the guest as MULTIuser. IBM Shared Tape Support imposes this MULTISYSTEM ASSIGN restriction, not CA MIA.

Important! The value of the GTAINIT ASSIGN parameter must be the same on all systems in the CA MIA complex for ASSIGN processing to work correctly. If you are changing the GTAINIT ASSIGN= parameter, then perform a GLOBAL SHUTDOWN. CA MIA will shut down on all systems in your complex, including systems that are not guests under z/VM. All tape devices managed by CA MIA should be offline on all systems with no tape activity to the devices, to clear the ASSIGNS from all of the devices. The MIMINIT member is updated to specify the GTAINIT ASSIGN=NOASSIGN parameter before restarting CA MIA on any system. Failure to follow this procedure can result in the inability to use tape devices on one or more systems in the complex.

If you are running in a CA MIA complex that includes both CA MIA and CA MIA for z/VM, then you should already be using the GTAINIT ASSIGN=NOASSIGN parameter on all systems, since the NOASSIGN parameter is required in a mixed CA MIA and CA MIA for z/VM environment.