Introduction › Multisystem Considerations

Multisystem Considerations

In a multisystem environment, the systems cannot concurrently access the physical tape data sets. A tape created on one system can only be read or modified on a different system after the first system releases the tape. Each CA Vtape subsystem can access a specific Virtual Volume as often as required. However, only one subsystem can access a specific Virtual Volume at a time.

You can simultaneously run up to eight CA Vtape subsystems within a single Logical Partition (LPAR). Each subsystem runs in its own set of address spaces and must be assigned a unique range of Virtual Device addresses. Once assigned and varied online by one of the subsystems, other subsystems in the same LPAR cannot use the same Virtual Device addresses.

The same Virtual Device address range can be defined on multiple LPARs for the use of a single CA Vtape subsystem on each LPAR. Do not define the devices as shared in the operating system hardware configuration definitions or in an automatic tape switching product such as CA MIA or IBM Tape Auto Switch. Virtual Devices 0100-010F on LPAR A are not the same Virtual Devices as 0100-010F on LPAR B because separate subsystems control them. Each of these devices can be online and actively servicing virtual tape mounts on both LPARs at the exact same time. The only restriction is that they cannot mount the same Virtual Volume simultaneously.

A CA Vtape Complex is created when multiple CA Vtape subsystems in the same LPAR or in different LPARs share the control data sets and the network appliance where the Virtual Volumes reside. The CA Vtape subsystems participating in a CA Vtape Complex can read or write any Virtual Volume data with any other subsystem participating within the same CA Vtape Complex.

A SYSPLEX is not required to support a CA Vtape Complex. Some CA Vtape features are not fully exploited unless CA MIM or IBM's GRS can propagate enqueues across all the LPARs where CA Vtape is implemented.