Defining the parameters of the recycle process

To define the parameters of the recycle process, you must specify the following information:

The maximum percent of data remaining valid on a full (backup or ML2) or partial (nonassociated ML2) tape volume and its connected set before the volume is recycled
The desired number of ML2 partial tape volumes not associated with any migration or recycle output task that remain after the recycle process
The kind of unit used for output in recycling tape volumes
Whether the recycle process waits for a tape allocation
How many recycle tasks can run concurrently
Whether to duplex recycle output. For ML2 tapes, specify SETSYS DUPLEX(MIGRATION(Y | N)). For backup tapes, specify SETSYS DUPLEX(BACKUP(Y | N)).

The SETSYS command is used for defining the default parameters of the recycle process. The command that is added to the ARCCMDxx member in each DFSMShsm host for the example system is:

SETSYS ML2RECYCLEPERCENT(25) RECYCLEPERCENT(25) -
   RECYCLEOUTPUT(BACKUP(ACL),MIGRATION(ACL)) -
   MAXRECYCLETASKS(3) ML2PARTIALSNOTASSOCIATEDGOAL(8)

The following discussions of the SETSYS parameters related to recycle processing use the term connected set. A connected set is a single tape or a group of 2 or more tapes that has the following properties:

The first tape has no valid data set spanning to a previous tape. (A spanning data set is a data set that is contained on more than one tape, and can span from 2 to 254 tape volumes.)
The last tape has no valid data set spanning to a successive tape.
All tapes have either a valid data set spanning to their previous tape, to their successive tape, or to both.
All tapes are of one function type (for instance, all migration tapes).
All tapes can be read on the same tape drive (for instance, a 3480X 18-track drive with IDRC compaction).
A valid data set is contained entirely in only one connected tape set.
DFSMShsm recycles only those that are 254 or fewer volumes long. For an ML2 partial tape to be considered, it must be the only tape in its connected set.

Input tape drives that are allocated for connected sets remain allocated until all input tapes have been processed.

ML2RECYCLEPERCENT and RECYCLEPERCENT control the maximum amount of data that is valid on ML2 volumes and backup volumes, respectively, when DFSMShsm automatically selects the volume for processing during recycling. In the example system, when DFSMShsm detects that it has invalidated enough data to bring the amount of valid data on a volume and its connected set to 25% or less, it writes an informational message in the command activity log. When the RECYCLE command is issued for the appropriate category of volume, DFSMShsm automatically selects each connected set of that category that has 25% or less valid data and recycles the complete connected set.

Note: For reel tapes, the percentage is valid blocks divided by total blocks written to this tape. For cartridge tapes, the percentage is valid blocks divided by estimated reuse capacity. This reuse capacity is estimated as the average total blocks written for each cartridge type.

The percentages for tapes can be displayed using either RECYCLE DISPLAY or LIST TTOC commands. (If you use the RECYCLE DISPLAY command, volumes which have 0 percent valid will not be listed. When such a volume is recycled, it will not be mounted, thus the volume does not have to be retrieved to be recycled.)

ML2PARTIALSNOTASSOCIATEDGOAL controls the desired number of partial ML2 tape volumes that are available. The recycle process considers all the ML2 partial tape volumes in the HSMplex that are not associated as output for any migration or recycle task and are not connected to a predecessor tape. If the number of those volumes is greater than eight, the excess volumes over eight are recycled. The tapes with the least amount of valid data (and that meet the other recycling criteria specified for the installation) are selected for recycling.

RECYCLEOUTPUT restricts the category of output device used by DFSMShsm for writing the tape volume that consolidates the data from the tape volumes being recycled. Because you want the output tapes mounted on the 3490 devices with the automatic cartridge loader feature, you use the esoteric name that was specified with the USERUNITTABLE parameter of the SETSYS command.

MAXRECYCLETASKS specifies the maximum number of tape processing subtasks that DFSMShsm will run. The default value is 2, and this value can be dynamically changed even while RECYCLE is running by using the SETSYS MAXRECYCLETASKS(nn) command (the minimum number of tasks is 1, the maximum number is 15). In the example system, MAXRECYCLETASKS is set to 3 subtasks (6 tape drives involved).

Note:

Each subtask requires two tape drives. If duplexing, each task requires three tape drives. One drive for the input tape, one for the original tape, and one for the alternate tape.
Each subtask, when dealing with single-file-format tape cartridges, keeps the input tape drive allocated for as long as possible (certain error conditions will cause the drive to be deallocated).

RECYCLETAPEALLOCATION specifies whether DFSMShsm is to wait for tape allocation to complete or is to proceed to process other requests. You have already specified NOWAIT in the initial overall SETSYS command.

Defining the parameters of the recycle process

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