Invoking the installation exit

This installation exit can be invoked during the following processing steps:

Job step setup
Device allocation
Library mount

The following conditions can cause invocation of the exit:

If some of the tape volumes in a multivolume tape data set are not resident in a tape library, the request would fail, because all the tape volumes belonging to the same multivolume data set must reside in the same tape library. The exit can be used to direct the missing tape volumes back into the library.
Note: In a multivolume data set request, during job step setup and device allocation processing, the exit is only invoked when the first volume of the data set does not reside in a tape library. However, later during library mount processing, the exit is invoked each time a multivolume data set volume is needed but does not reside in the tape library. The exit can wait until library mount processing to get the additional volumes entered on an "as needed" basis, or if it is known that specific applications always use the entire multivolume data set, the exit, during job step setup, can instruct the operator to enter all volumes of the multivolume data set. The choice is determined by the exit. However, keep in mind that the exit is only passed one volume serial number at a time, and is not passed all the volumes in the multivolume data set, nor is it passed any data set information.
If none of the tape volumes reside in a tape library, or the tape volumes were previously resident in a tape library but are currently shelf-resident, they are considered non-SMS managed tape volumes and are allocated to a tape drive of the appropriate device type outside a tape library. The exit can be used to enter the tape volumes into a tape library.
For example, if the only 3490E tape drives that an installation has are inside a tape library, then whenever a shelf-resident enhanced capacity cartridge system tape is requested, it must be entered into a tape library containing a 3490E tape drive. The exit can be used to direct the enhanced capacity cartridge system tape into a library that is capable of handling the request.

Note: Before invoking the exit during job step setup, OAM does not know if there are any stand-alone drives capable of handling the volume. The exit is invoked to report that the tape volume is not in a tape library, and it allows the exit to decide whether the volume should reside in a tape library, and if so, which tape library should be used.
If a tape volume is ejected from a tape library between job step setup and library mount processing, the request requiring the tape volume would fail. The exit can reenter the required tape volume into the specified tape library to prevent the job from failing.
However, if a logical volume is being exported from a tape library dataserver between job setup and library mount processing, the mount request immediately fails, since an export operation is not immediate.

Note: The input to the exit at device allocation does not identify the library to which the tape volume must return, because the information was erased when the volume was ejected from the library. Therefore, the exit must rely upon other sources to determine which library should receive the missing volume.
If tape volumes are not library-resident in a tape library and are physically located in a remote area, requests for these volumes are allocated to stand-alone tape drives and are delayed until the volumes are retrieved and mounted on the stand-alone tape drives. While jobs are waiting for these tape volumes to be mounted, the system resources allocated to these tape volumes are unavailable for use by other jobs. CBRUXVNL can identify this condition and interact with the installation’s tape management system to determine the best course of action to alleviate this waste of time and resource.
Since the ATLDS has a finite tape cartridge capacity, infrequently used tape volumes may be ejected until their next scheduled use. These tape cartridges should be reentered in advance of reuse to avoid job processing delays, but since this is not always possible, this exit can be used to identify and correct this condition, preventing job failures.
Note: With JES3, the job step notification occurs before the job being scheduled for execution. Therefore, missing tapes can be located and entered into the tape library well in advance of usage.