Draft Document for Review February 7, 2020 3:15 pm 8464ch04_Planning.fm If tape libraries are shared among hosts that are all intended to have access to the same  volumes, they must all use a single TCDB on shared disk. Each such TCDBplex must have a  unique  DEVSUPxx  parmlib member that specifies library manager categories for each scratch  media type, error, and private volumes.  It is always recommended to change the IBM-supplied DEVSUPxx parmlib member to have  site-specific values. Even if this member is shared between all hosts, it is advisable not to use  the default categories because the use of such categories complicates debugging of any  cartridge entry problems.  Planning what categories are used by which hosts is an important consideration that must be  addressed before the installation of any tape libraries. For more information about OAM  implementation and category selection, see  z/OS DFSMS OAM Planning, Installation, and  Storage Administration Guide for Tape Libraries , SC23-6867. The virtual drives and virtual volumes in a TS7700 can be partitioned just like physical drives  and stacked volumes, although by way of different mechanisms. Any virtual volume can be  directed to any physical stacked volume when you use a TS7700T. The TS7700 places no  restrictions on the use and management of those resources. When you use a TS7700T, you  can partition your stacked volumes in up to 32 separate pools by assigning a volume range to  a pool and that pool to an SG before insertion time of the physical stacked volume. Partitioning the physical media between multiple hosts 4.3.5 Library Manager Category Usage Considerations 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. 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 that are associated with a system or sysplex, or both.  It is the responsibility of the installation to ensure that all systems or sysplexes (or both) that  are associated with the same TCDB (TCDBplex) use the same category assignments. For  more information about the partitioning-related DEVSUPxx parameters, see  z/OS MVS  Initialization and Tuning Reference , SA23-1380. In a partitioned library, it is recommended that the installation use DEVSUPxx to change the  default categories that are associated with each TCDBplex. Therefore, because no TCDBplex  uses the default categories, no volumes are 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 a  TCDBplex uses the default categories, volumes can 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 because no tape volume record is 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. Chapter 4. Preinstallation planning and sizing  173