Optimizing cartridge loaders by restricting output to devices with cartridge loaders

DFSMShsm always requests a mount for a specific tape for input processing, so cartridge loaders are of little value for input. For mounting a single tape on a 3480 device type from which to recall or recover a data set, it may be more economical to allocate a device that does not have a cartridge loader.

To ensure that non-cartridge-loader devices are used for input, you can direct DFSMShsm to use esoteric unit names in a special way that directs a cartridge to be allocated on a different set of devices for input than was used for output. This activity is called esoteric translation and it occurs if:

You have specified an esoteric unit name that is associated with a group of output devices.
The output devices associated with the esoteric unit name are online when the SETSYS USERUNITTABLE command is specified. Esoteric translation is not dynamic and DFSMShsm knows only the devices that are online at the moment the SETSYS USERUNITTABLE command is issued.
All devices associated with the esoteric unit name have cartridge loaders. For the exception, see Removing ACL as a condition for D/T3480 esoteric unit name translation.

Only if the preceding conditions have been met can esoteric translation occur. Esoteric translation occurs in either of two ways:

If you specify the translation name, DFSMShsm retains the new unit type for input allocations of the tape.
If you do not specify the translation name, DFSMShsm retains the generic unit type of the output esoteric for output allocations of the tape.

If you specify . . .	Then . . .
SETSYS USERUNITTABLE (ACLOUT:ACLIN)	And all of the preceding conditions have been satisfied, a tape is allocated on a different set of devices for input than was used for output.