TAPEUTILIZATION: Specifying the desired tape utilization

Explanation: TAPEUTILIZATION is an optional parameter you can use to specify the desired tape utilization for a backup or migration tape volume written in single-file format. When a single-file format tape volume has reached the desired level of utilization (fullness), DFSMShsm forces an end-of-volume (EOV). With this parameter, you can limit the amount of media used.

LIBRARYBACKUP is a mutually exclusive, required subparameter used to specify the desired tape utilization for a backup tape stored in an SMS-managed tape library. Because esoteric unit names are ignored in an SMS-managed tape library, this is the only vehicle by which you may limit the amount of media used in a library backup cartridge. PERCENTFULL(pct) and NOLIMIT are mutually exclusive, optional subparameters that can be used with LIBRARYBACKUP.

LIBRARYMIGRATION is a mutually exclusive, required subparameter used to specify the desired tape utilization for a migration tape stored in an SMS-managed tape library. Because esoteric unit names are ignored in an SMS-managed tape library, this is the only vehicle by which you may limit the amount of media used in a library migration cartridge. PERCENTFULL(pct) and NOLIMIT are mutually exclusive, optional subparameters that can be used with LIBRARYMIGRATION.

UNITTYPE(unittype) is a mutually exclusive, required subparameter used to specify the desired tape utilization for a backup or migration tape written in single-file format outside of any library. PERCENTFULL(pct) and NOLIMIT are mutually exclusive, optional subparameters that can be used with UNITTYPE.

This command can be issued multiple times, once for each unittype required. You must issue this command for each unique unit type that needs a percentage different from the default. For example, if both 3480s and 3490s exist, issue a separate SETSYS TAPEUTILIZATION command. Issue a separate command for a different esoteric unittype. For example, if separate esoteric unit names are used for backup and migration, each one can have a different tape utilization value.

For unittype, specify one of the following unit names:

3480, which is a 3480 without the IDRC
3480X, which is a 3480 with the IDRC
3490
3590-1
Any esoteric name that has been identified to DFSMShsm through the SETSYS USERUNITTABLE command.

If NOLIMIT is specified, there is no tape limiting, no action is taken to reduce data set tape volume spanning and DFSMShsm writes data until the end-of-volume is reached. It is recommended that you specify PERCENTFULL(100) on the SETSYS TAPEUTILIZATION command when reduced data set tape volume spanning is needed. Specifying NOLIMIT will disable reduced data set tape volume spanning.

CAPACITYMODE(COMPATIBILITY | EXTENDED) is an optional subparameter you can use to specify the maximum capacity to which a tape is filled. COMPATIBILITY specifies that an IBM® 3590 that emulates an IBM 3490 fills a tape to no more than the capacity allowed by an IBM 3590 that emulates an IBM 3490 that is not operating in extended capacity mode. Data on these tapes is accessible to IBM 3590 drives that emulate IBM 3490 drives, regardless of whether they are CAPACITYMODE switchable. EXTENDED specifies that an IBM 3590 that emulates an IBM 3490 fills a tape to the same capacity as 3590 drives allow. Data on these tapes is accessible only to tape units that are CAPACITYMODE switchable.

The CAPACITYMODE subparameter is valid when all the following are true:

CAPACITYMODE is used in conjunction with UNITTYPE
The subparameter of UNITTYPE is an esoteric that is specified through SETSYS USERUNITTABLE
The UNITTYPE contains only IBM 3590 drives that are emulating IBM 3490 drives that are CAPACITYMODE switchable.

When you specify CAPACITYMODE incorrectly, DFSMShsm ignores the subparameter. For example, if you specify CAPACITYMODE when the UNITTYPE is a generic, such as 3490, DFSMShsm ignores the CAPACITYMODE subparameter. Also, if you specify CAPACITYMODE for an esoteric capable of CAPACITYMODE(EXTENDED), but you do not specify COMPATIBILITY or EXTENDED, CAPACITYMODE is ignored.

SMS relationship: Parameter has the same meaning when applied to SMS-managed or non-SMS-managed DASD volumes or data sets.

SETSYS default: None.

DFSMShsm default: For TAPEUTILIZATION the DFSMShsm default value is 97%. If you use the DFSMShsm default value, the data on one cartridge can most likely be copied to another cartridge of the same category. If you do not plan to copy cartridges, you might specify NOLIMIT to use the entire cartridge capacity. However, it is recommended that you instead specify PERCENTFULL(100) to get the benefits of reduced tape spanning.

For TAPEUTILIZATION CAPACITYMODE, the DFSMShsm default is COMPATIBILITY. During an input operation, DFSMShsm temporarily switches the unit to CAPACITYMODE(EXTENDED) if it is given a tape in that mode. If you do not specify CAPACITYMODE for an esoteric capable of CAPACITYMODE(EXTENDED), during a DFSMShsm output function, the drives operate in CAPACITYMODE(COMPATIBILITY).

Note:

In a duplex tape environment, DFSMShsm uses the default PERCENTFULL value of 97 percent. This value is not likely to be a problem unless you are targeting a 3590-Bx or vendor drive in 3490 emulation mode. These drives need a percent value of a few hundred to fully utilize the tape's capacity. A value of 97 percent is appropriate, however, for targeting a 3590-Ex drive, even if in 3490 emulation mode.
Issuing the SETSYS USERUNITTABLE command will reset the TAPEUTILIZATION for all esoteric devices to the DFSMShsm default of 97 percent. For the command to be effective, you must enter the SETSYS USERUNITTABLE command before the SETSYS TAPEUTILIZATION command.
UNITTYPE(unittype), LIBRARYBACKUP, and LIBRARYMIGRATION are mutually exclusive subparameters. A separate SETSYS command must be issued for each subparameter. For example, to use 100% of the capacity but retain the reduced tape spanning, issue the following commands:
```
SETSYS TAPEUTILIZATION(UNITTYPE(unittype) PERCENTFULL(100))
SETSYS TAPEUTILIZATION(LIBRARYBACKUP PERCENTFULL(100))
SETSYS TAPEUTILIZATION(LIBRARYMIGRATION PERCENTFULL(100))
```
For drives prior to the IBM 3590 Model E1x, DFSMShsm based the PERCENTFULL value on the cartridge type of the reported logical device type in emulation mode. For IBM 3590 Model E1x drives, DFSMShsm uses the reported cartridge type of the physical device to determine the tape capacity. When using these tape drives, you do not need to supply a percentage greater than 100 to reasonably fill the tapes. As a result, DFSMShsm has improved the ability to fill migration and backup tape cartridges when using IBM 3590 Model E1x drives.
If you have tape cartridges that have a capacity larger than the IBM enhanced-capacity tape cartridges, it is recommended that you specify the PERCENTFULL(pct) parameter for the unit type when those tapes will be used instead of specifying NOLIMIT. For pct, specify a value between 1 and 9999.
For example, if you have tape cartridges that are approximately 25% larger, using a value of PERCENTFULL(122) on the SETSYS TAPEUTILIZATION command is recommended for the following reasons:
- You want to avoid hitting the natural EOV because that would tie tapes together and until the spanning data set is invalidated, all the tapes containing the desired data set must be handled to access the one spanning data set.
- RECYCLE has to treat the connected tapes together until the spanning data set is invalidated. This process generally delays the tapes from being returned to scratch.
- A chain of 240 connected tapes will likely be created if TAPEUTILIZATION is not used. If you have an error and need to take some explicit corrective action on one tape, you may have to process a very long chain of tapes.
- The TAPECOPY function will probably be able to copy these tapes but only to similar or larger tapes. However, the use of 122% rather than 125% increases the possibility of a successful tape copy by maintaining an equivalent 97% tape utilization.

IBM 3590 drives introduce a new microcode support; see Table 1 for the percent values to use with the SETSYS TAPEUTILIZATION command:

Table 1. Tape Utilization Capacity for MEDIA3 or Greater.
Percent to use	3490 Mode	3590 Mode
3590B with MEDIA3 or MEDIA4	2200. If any of the 3590B drive controllers are running with a level of microcode prior to 1.9.19.0, use a value of 1100 instead.	97
All others	97	97

DFSMShsm writes to 97% of the capacity of MEDIA5, MEDIA6, MEDIA7, MEDIA8, MEDIA9, MEDIA10, MEDIA11, MEDIA12, and MEDIA13 tapes unless otherwise specified by the installation. Other percentages can be specified through the SETSYS TAPEUTILIZATION command, depending on the particular needs of the installation. DFSMShsm uses the reported cartridge type on the physical device to determine the tape's capacity.