MVS device allocation helps prioritize and select tape drives to meet the needs of application programs or system functions. Batch (JCL) or dynamic (SVC99) allocation makes these device needs known to MVS device allocation. MVS device allocation selects the appropriate devices and serializes them for the requester to use. It can also request that appropriate volumes be mounted on the allocated devices. It accomplishes these tasks by interfacing with SMS, DEVSERV, OAM, MSGDISP, and other system components.

MVS device allocation currently supports multiple types of tape devices. Within an IBM tape library environment, MVS device allocation considers media types and recording technologies when allocating tape drives and tape volumes. The dynamic allocation (SVC 99) volume interchange text unit (DALINCHG) allows you to specify EFMT1 for the recording technology and MEDIA5, MEDIA6, MEDIA7, or MEDIA8 for the media type and EFMT2 or EEFMT2 for the recording technology and MEDIA5, MEDIA6, MEDIA7, MEDIA8, MEDIA9 and MEDIA10 for the media type. Specification of MEDIA9 or MEDIA10 is only supported on z/OS V1R5 and above.

See Table 1 for DALINCHG parameter values.

Related reading:

• See z/OS MVS System Commands for more information on the DEVSERV QTAPE command.
• See z/OS MVS Programming: Authorized Assembler Services Guide for more information about the DALINCHG parameter.
• See z/OS DFSMS Installation Exits for more information about the IECUCBCX mapping macro.