To partition a library among multiple TCDBplexes requires separation of the scratch pools; that is, each TCDBplex must have a separate library manager category for each scratch media type. For logical completeness, the error and private volume categories should also be unique to each TCDBplex. The default category assignments are described in Table 1.

To change the default category assignments, specify the categories in PARMLIB member DEVSUPxx. The category specification parameters enable the installation to change the default category assignments associated with a system or sysplex, or both. It is the responsibility of the installation to ensure that all systems or sysplexes, or both, associated with the same TCDB (TCDBplex) use the same category assignments. For a discussion of the partitioning-related DEVSUPxx parameters, see z/OS MVS Initialization and Tuning Reference.

In a partitioned library, it is recommended that the installation use DEVSUPxx to change the default categories associated with each TCDBplex. This means that no TCDBplex uses the default categories, so there are no volumes in those categories. If the DEVSUPxx parameters are inadvertently removed from one system, scratch mount requests are directed to the empty default categories and the mount requests fail. If there is a TCDBplex that is using the default categories, volumes may be mounted by the system where the DEVSUPxx parameters were removed. If a scratch volume from a default category is mounted on the system where the parameters were removed, it is not used since there is no tape volume record in the TCDB. The volume is assigned to the error category with resultant disruption in library operations in the TCDBplex that owns the default categories.