The volume not in library installation exit (CBRUXVNL) receives control under a variety of circumstances and error conditions that occur during job processing. The primary purpose of the exit is to give the installation the opportunity to enter a volume into a tape library during job step setup, device allocation and library mount processing.

If a tape is inadvertently ejected from a tape library, the exit is invoked providing an opportunity to reenter the volume in the library. With this support, job-related information is passed to the exit, via the CBRUXNPL parameter list, increasing the length of the parameter list. Job-related information can be used to assist the exit in making better decisions on whether to enter the volume in a library or take other action such as cancel the job or allow the allocation to select a standalone drive. The UXNJINFO indicator in the CBRUXNPL parameter list is set on when the CBRUXVNL installation exit is invoked during job step setup processing and job information is provided in the UXNJOB job information fields. If the UXNJINFO indicator is not on, then either the job information is not available because the CBRUXVNL exit invocation is not for job step setup processing or the system does not have the volume not in library job information support installed. If job information is available (job step setup CBRUXVNL invocation) but the information for a job information field is not available, the field contains binary zeroes. The new job-related information is only passed to the volume not in library exit during the job step setup invocation as this is the critical time for the exit to determine if the volume should be entered into a library. For the other phases of processing (device allocation and library mount processing), it has already been determined that the volume should reside in a tape library and timing was such that the volume was ejected. Since a failure to enter the volume into a tape library or the library specified during the device allocation or library mount phases of processing would result in job failures, the additional job-related information is not needed for those phases of processing.

If UXNJOB job information is available (job step setup CBRUXVNL invocation) but the information for a job information field is not available, generally, the field contains binary zeroes. The UXNDISP fields contain standard JCL disposition parameters (status, normal, abnormal), reflecting the job specifications. If not specified on the job invocation, UXNDISP1, UXNDISP2, and UXNDISP3 may contain zeroes or, in some cases, may contain default disposition settings rather than zeroes. If the CBRUXVNL installation exit is invoked and the job-related information is for a volume that is part of a concatenated data set DD statement and is not the first data set in the concatenation, the UXNDDNM field will contain blanks.

For old allocations, if a volser was not specified and the dataset is cataloged, then the UXNCATLG indicator is set "on" and the UXNDEVTP field contains the 4-byte device type from the catalog. Otherwise, the UXNCATLG indicator is "off" and the UXNDEVTP field contains zeroes. When unit information is available (UNIT=), the UXNUNIT field contains the passed value; otherwise, the UXNUNIT field contains zeroes.

For more information regarding the CBRUXVNL installation exit, please see z/OS DFSMS OAM Planning, Installation, and Storage Administration Guide for Tape Libraries.