IBM 3590 capacity utilization considerations

Allowing IBM® 3590 tape drives that emulate IBM 3490 tape drives to operate in COMPATIBILITY mode makes coexistence possible in an HSMplex until you have updated all of your systems. The use of the SETSYS TAPEUTILIZATION(CAPACITYMODE) parameter makes this possible.

If you install this IBM 3590 CUPE support on one DFSMShsm at a time, run the supported hosts with CAPACITYMODE(COMPATIBILITY) specified until you install the IBM 3590 CUPE support across the entire HSMplex. Then all or any combination of hosts in the HSMplex can run with CAPACITYMODE(EXTENDED) specified.

Note: Recall and recover fail with an error message when any DFSMShsm task in a system that does not have access to an esoteric with CAPACITYMODE switchable drives and the data set is on a CAPACITYMODE(EXTENDED) tape. Any system running with CUPE coexistence support fails the recall or recover function when a needed data set is on a CAPACITYMODE(EXTENDED) tape.

In order for DFSMShsm to recognize that a drive has the CAPACITYMODE(EXTENDED) function, that drive must have been online at least once since IPL. This is a new requirement. The system programmer might chose to cause all drives to be online at IPL or to issue VARY ONLINE commands automatically.

High capacity tapes are more fully utilized when you specify the CAPACITYMODE(EXTENDED) parameter for that defined esoteric. If a DFSMShsm function needs to mount a tape that was created with CAPACITYMODE(EXTENDED) specified but no CAPACITYMODE switchable drives are available, the DFSMShsm function fails with an error message. MEDIA3 and MEDIA4 tapes that are filled when the CAPACITYMODE(COMPATIBILITY) parameter is specified, can be read by all IBM 3590 drives emulating IBM 3490 drives regardless of the CAPACITYMODE switchable capability as long as the recording technologies are read compatible.

Rule: To return to a CAPACITYMODE(COMPATIBILITY) environment, you must reissue the SETSYS TAPEUTILIZATION(CAPACITYMODE(COMPATIBILITY)) command so that no new data is written in CAPACITYMODE(EXTENDED) format.