Considerations for using the 3592 Model J tape drive

Here are some tips you might find helpful when using the 3592 Model J tape drive.

If your installation has an excessive number of spanning data sets, consider specifying a larger value in the SETSYS TAPESPANSIZE command. A larger absolute value is needed to represent the same amount of unused capacity on a percentage basis when the tape has a larger total capacity. For example, if you allow 2% of unused tape to avoid tape spanning for a 3590-Hxx device using enhanced media, you specify a TAPESPANSIZE of 1200 MB. To allow 2% unused tape for a MEDIA5 tape on a 3592 Model J device (no performance scaling), you specify a TAPESPANSIZE of 6000 MB. All size calculations for scaled tapes are based upon the scaled size and not the unscaled size.
If the speed of data access on MEDIA5 tape is more important than full use of capacity, consider using performance scaling. Performance scaling allows 60 GB of physical (and more logical) data on each tape and keeps all data sets closer together and closer to the initial tape load point. If you use performance scaling with the DFSMShsm duplex function, ensure that the original tape and the alternate tape both use performance scaling. Similarly make sure that Tapecopy input tapes and output tapes have the same performance scaling attributes.
Note: Performance scaling is not available on MEDIA6, MEDIA7, or MEDIA8 tape cartridge media.
If your installation is using MEDIA5 tapes with performance scaling, consider using MEDIA7 tapes for high performance functions. The available MEDIA5 tapes could then be used to their full capacity. DFSMShsm recycle processing of 3592 tapes can take significantly longer than the recycle of smaller tapes because the amount of data moved at the same RECYCLEPERCENT can be much larger. Besides moving more data, the likelihood of a tape takeaway for recall processing increases with the number of data sets still remaining on the tape.
One option for controlling overall recycle run time is the LIMIT(nnnn) parameter of recycle. Recycle returns no more than the specified number of tapes to scratch during the current recycle run. Because recycle sorts the tapes based on the amount of valid data still on each volume, the tapes recycled require the least processing time.

Another option to consider is decreasing the ML2RECYCLEPERCENT parameter, the RECYCLEPERCENT parameter, or both. For example, if your installation uses performance scaling (60 GB) for ML2, and you would like to move no more than 6 GB of data when an ML2 tape is recycled, set ML2RECYCLEPERCENT(10). If your installation uses full capacity (300 GB) for backup tapes and you would like to move no more than 6 GB of data when a backup tape is recycled, set RECYCLEPERCENT( 2). These examples assume that the ML2 and Backup tapes in the installation are filled to capacity because the calculations are based upon the average fullness of marked full tapes on your system (the reuse capacity.)

To determine how much data your current recycle threshold implies, use the reuse capacity associated with the tapes. The current recycle threshold percent multiplied by the reuse capacity gives the maximum amount of data on any of the tapes when they are recycled.

While lowering the recycle threshold reduces recycle processing time and decreases the number of times each tape must be recycled, it may also increase the overall number of tapes needed in your installation. Also, if you have a mix of ML2 or Backup tape capacities in need of recycle processing, you may want to recycle tapes with the RANGE parameter and use the appropriate recycle threshold for the tape capacities in the range.

In an SMS tape environment, and optionally in a non-SMS tape environment, the SMS data class construct can be used to select WORM tapes for ABACKUP processing. The output data set prefix specified in the aggregate group definition can be used by the ACS routines to select a WORM data class. Set up the ACS routine and the output data set name to uniquely identify the ABARS output files that must go to WORM tape.

In a non-SMS tape environment, the default is to allow tape pooling to determine if ABARS data sets go to WORM or R/W media. Optionally, if the DEVSUP parameter ENFORCE_DC_MEDIA=ALLMEDIATY or ENFORCE_DC_MEDIA=MEDIA5PLUS is used, then the data class must request the appropriate media type for it to be successfully mounted.
If your installation is running z/OS® in a Sysplex environment, consider using the Common Recall Queue to optimize mounts of migration tapes.
AUDIT MEDIACONTROLS for a FAILEDCREATE situation typically only needs to look at the last few files on a tape. If it is available for your system level, make sure Audit APAR OA04419 is applied.
To fully use MEDIA5 tapes, unless you have a specific need to run in 22-bit FBID mode, operate 3592 Model J tape drives emulating device type 3490 in 32-bit FBID mode. MEDIA6, MEDIA7, and MEDIA8 tapes cannot be used on a 3592 Model J emulating device type 3490. The 3592 Model J tape drive always operates in 32-bit FBID mode when it is emulating device type 3590.
If you decide to change the performance scaling attribute for a particular function and partially full MEDIA5 tapes already exist, mark full the partial MEDIA5 tapes for that function. This is necessary because OPEN processing carries over the performance scaling attribute from partial tapes to the next mounted empty tape as long as the tape is mounted under the same allocation. When the function runs the next time, it will need to mount an empty tape and the performance scaling change can take effect.