PARTIALTAPE: Specifying whether to reuse partially full tapes

Explanation: PARTIALTAPE is an optional parameter specifying that you want DFSMShsm to mark a cartridge-type single-file formatted tape volume full when the volume has been demounted.

MARKFULL and REUSE are mutually exclusive parameters of the PARTIALTAPE parameter. One of these parameters must be specified if the PARTIALTAPE parameter is specified. If not, an error message is issued.

Subparameter	Explanation
MARKFULL	DFSMShsm automatically marks a single-file-formatted tape volume full (except after data set migration or data set backup) independent of the block count when it demounts the tape. These volumes can be marked as full even though the volume is only partially used. DFSMShsm excludes data set migration or backup to avoid marking a tape volume full after a command migration or after a command backup of a single data set to migration level 2. When running in a PARTIALTAPE(MARKFULL) environment, a generic TAPECOPY command will select, copy, and mark full nonduplexed original tapes that are not marked as full, even if an alternate tape volume serial number is already recorded in the DFSMShsm inventory (TTOC record). In this case the older alternate is removed from DFSMShsm's inventory but not explicitly communicated to tape management products as with the ARCTVEXT exit method. DFSMShsm creates the new alternate because the partial original may have been extended after the old alternate was created by an explicit TAPECOPY. The older alternate is not communicated to tape management products so that the customer can retain alternates in addition to the one DFSMShsm maintains. DFSMShsm issues an ARC0436I message to the console and identifies the old alternate, the original, and the new alternate. Customers can update their tape management product if they do not want to retain the old alternates.
REUSE	DFSMShsm uses the normal process of marking a single-file formatted tape full only when the percent full (specified with the SETSYS TAPEUTILIZATION parameter) is reached.

Subparameter

Explanation

MARKFULL

DFSMShsm automatically marks a single-file-formatted tape volume full (except after data set migration or data set backup) independent of the block count when it demounts the tape. These volumes can be marked as full even though the volume is only partially used. DFSMShsm excludes data set migration or backup to avoid marking a tape volume full after a command migration or after a command backup of a single data set to migration level 2.

When running in a PARTIALTAPE(MARKFULL) environment, a generic TAPECOPY command will select, copy, and mark full nonduplexed original tapes that are not marked as full, even if an alternate tape volume serial number is already recorded in the DFSMShsm inventory (TTOC record). In this case the older alternate is removed from DFSMShsm's inventory but not explicitly communicated to tape management products as with the ARCTVEXT exit method. DFSMShsm creates the new alternate because the partial original may have been extended after the old alternate was created by an explicit TAPECOPY. The older alternate is not communicated to tape management products so that the customer can retain alternates in addition to the one DFSMShsm maintains. DFSMShsm issues an ARC0436I message to the console and identifies the old alternate, the original, and the new alternate. Customers can update their tape management product if they do not want to retain the old alternates.

REUSE

DFSMShsm uses the normal process of marking a single-file formatted tape full only when the percent full (specified with the SETSYS TAPEUTILIZATION parameter) is reached.

If you specify the global PARTIALTAPE(MARKFULL | REUSE) parameter, the parameter applies to both migration and backup. If you specify a specific function, the parameter applies only to that function. If you specify a global value and a specific function in a single command, the command will fail.

The PARTIALTAPE(MIGRATION(...)) parameter applies to tape volume migration only. The PARTIALTAPE(BACKUP(...)) parameter applies to tape volume backup only.

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: The default is REUSE, meaning that DFSMShsm marks the tape volume full only when the volume reaches the maximum block count specified with the SETSYS TAPEUTILIZATION parameter.

Note: If you are using a VTS subsystem for migration or backup output, the MARKFULL parameter can improve performance by reducing the need to remount yesterday's partial volume in order to extend it today. Additionally, this usage can somewhat reduce the reclamation process of the VTS subsystem because the physical tape containing the initial partial tape, that was extended, was not invalidated on a true tape.