Partitioning tape libraries among multiple sysplexes (systems)

Partitioning a tape library is dividing the resources in the library—tape drives and tape volumes—among multiple systems or sysplexes, or both, for their exclusive use. The set of tape drives and tape volumes which belong to one or more systems or sysplexes, or both may not be used by a nonsharing system or sysplex without manual intervention. Each sharing partition may be either an MVS platform or a non-MVS platform. A single MVS platform may consist of one or more systems or sysplexes, or both, connected to a shared tape configuration database (TCDB); this group of sharing systems or sysplexes, or both, is referred to as a TCDBplex. Multiple TCDBs may each contain configuration information about the library and some subset of the volumes in the library. Partitioning may thus be viewed as dividing a physical or virtual library into multiple logical libraries, with each logical library (TCDBplex) represented by one TCDB. Figure 1 provides a pictorial description of library partitioning.

Note: The scratch category thresholds and counts are maintained (for each tape library) in a tape library record in the TCDB (hlq.VOLCAT.VGENERAL). In a tape library record, there is only one set of scratch values for each media type, so sharing the same tape library record with other sysplexes (or systems) that are not using the same scratch categories can cause scratch threshold and possible load balancing issues across multiple libraries. When logically partitioning a tape library there must be a separate hlq.VOLCAT.VGENERAL for each set of sharing systems, so that each set of sharing systems can be managed by its own tape library record. This ensures that the scratch counts (in a tape library record) are tied to one set of scratch categories.

Figure 1. Partitioning a Tape Library