Partitioning system-managed tape libraries

You can partition a system-managed library including a VTS by performing these tasks:

Specify the USE operand value on the RMM ADDVOLUME or RMM CHANGEVOLUME subcommands. You can set this value to MVS or VM or both. If you do not specify MVS for a volume, DFSMSrmm prevents the volume from being defined in the volume catalog on this system.
Through the use of the PRTITION and OPENRULE parmlib commands, you can simplify the maintenance of the parmlib members as your libraries and volume ranges change. Operands on the OPENRULE and PRTITION commands allow global actions to be set. You can use one or more specific overrides based on volume sets that have different requirements. Typically, you could add a new range of volumes for use by a single partition and only that one system would need to be updated. The OPENRULE and PRTITION commands allow you to define whether they apply to volumes defined to DFSMSrmm or not. You can use operands on the OPENRULE command to automatically ignore volumes, rather than using EXPDT=98000 or a customized EDGUX100.
Note: PRTITION is the preferred method for partitioning. REJECT commands, although still supported, should not be used in new installations. If you use REJECT commands, you have to convert from the use of REJECT commands in order to use the PRTITION and OPENRULE commands. See Converting REJECT commands to PRTITION and OPENRULE commands for information about converting from the use of REJECT commands.

When you enter a volume into a system-managed tape library, if the volume is defined to DFSMSrmm and you have specified the USE operand without MVS, or the volume matches an OPENRULE specification that prevents a volume from being defined in the system-managed tape library on the current system, EDGLCSUX sets a return code of 12 to pass to OAM. OAM leaves the volume in the system-managed tape library in the INSERT category; it does not create a volume entry in the TCDB. The volume is then available for another sharing system to process the insert request. The sharing system could be another VM or z/OS system.

If DFSMSrmm allows the volume entry to be performed, OAM creates an entry in the TCDB. If the volume matches an OPENRULE specification that limits the volume's use to input processing, at OPEN time DFSMSrmm fails any requests for output processing, while allowing requests for input processing.

Using the PRTITION commands, you can control partitioning entry/insert, export/import, eject, and CUA processing for system managed volumes:

DFSMSrmm partitioning is based on a global setting that you can change. The default is that all system-managed and non-system managed volumes are accepted. This can be represented by this command:
```
PRTITION VOLUME(*) TYPE(ALL) SMT(ACCEPT) NOSMT(ACCEPT LOCATION(SHELF))
```
You can change the global setting so that all volumes are ignored by using this command:
```
PRTITION VOLUME(*) TYPE(ALL) SMT(IGNORE) NOSMT(IGNORE)
```
Using a global command like this:
```
PRTITION VOLUME(*)  TYPE(NORMM) SMT(IGNORE) NOSMT(IGNORE)
```
- All system-managed volumes undefined in the DFSMSrmm CDS are left in insert category to be accepted by another system and non-system-managed volumes are not added automatically to the CDS.
- The remainder of the default command [PRTITION VOLUME(*) TYPE(RMM) SMT(ACCEPT) NOSMT(ACCEPT)] that is not overridden by your global commands in parmlib is used to handle TYPE(RMM) volumes.
- With this approach, you must predefine system-managed volumes to DFSMSrmm to enable ownership of volumes during entry/insert processing.
No PRTITION commands - When REJECT commands are used, processing is as for earlier releases unless any OPENRULE statements are defined. In the latter case and when no REJECT commands are defined, the defaults are used for partitioning.
Using selective PRTITION statements on top of a global command, you can be very specific about which volumes are to become owned by the current system/partition.
- All ACCEPTed volumes that are not defined to DFSMSrmm are added automatically to the DFSMSrmm CDS and owned by this system/partition, unless it is eject processing.
  - For system-managed volumes, 'Owned by this system/partition' means that the volume is defined to DFSMSrmm, has an entry in the TCDB, and the scratch category used by the Library Manager (LM) is set based on your values in this systems DEVSUPxx.
  - The ISMF library default entry status is used for added volumes.
- Pre-defined volumes are only considered when the PRTITION command specifies TYPE(RMM) or TYPE(ALL). The volume status for the TCDB entry is set by DFSMSrmm from the volume information.

As a result of this flexibility, you should no longer need to customize the CBRUXENT exit.

In addition to the system-managed processing, the PRTITION commands also allow all volumes to be partitioned during inventory management and during OPEN processing. During EXPROC return to scratch processing, a volume matching to a PRTITION command with TYPE(ALL/RMM) and an action of IGNORE causes the return to scratch processing for the volume to be skipped. This occurs even if a TCDB volume entry exists (for example, the TCDB is shared or a TCDB entry was created manually for private volume sharing).

You can use the DFSMSrmm unshared catalog support, by means of OPTION CATSYSID, to control which volumes are processed on which system. For each scratch candidate volume, DFSMSrmm:

Checks PRTITION commands. If they are not ignored or skipped, DFSMSrmm continues with the next check.
Checks that a TCDB entry exists if system-managed. If yes, DFSMSrmm continues with the next check. If no, DFSMSrmm skips the volume.
Checks the unshared catalog. If the first file data set was not created on one of the CATSYSID systems, DFSMSrmm skips the volume.

You must run EXPROC once per scratch category set that you use for system-managed library partitioning.