Considerations for using the 3592 Model E07 tape drive

Here are some tips you might find helpful when using DFSMShsm with the 3592 Model E07 tape drive.

• In a non-SMS mixed tape hardware environment, where multiple types of tape hardware are used to emulate 3590 devices, it is recommended that you define unique esoterics for each type of tape hardware. This action is necessary to avoid mixing incompatible recording technologies. You can define an esoteric to DFSMShsm through the SETSYS USERUNITTABLE command, for example:

  SETSYS UUT(3592E07:3592E07 3590H:3590H)

  With esoterics defined, you can then direct output to the desired set of drives through the SETSYS command, for example:

  SETSYS BACKUP(TAPE(3592E07))

• 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, specify a TAPESPANSIZE of 1200 MB. To allow 2% unused tape for a MEDIA11 tape on a 3592 Model E07 tape drive (no performance scaling), specify a TAPESPANSIZE of 9999 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 a tape is more important than full use of capacity, consider using performance scaling, if the media you are using supports it. Performance scaling uses 20% of the physical capacity 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, be sure 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 the following tape cartridge media: MEDIA6, MEDIA7, MEDIA8, MEDIA10, MEDIA12, and MEDIA13.
• If you are using MEDIA5, MEDIA9, or MEDIA11 tapes with performance scaling, consider using MEDIA7 or MEDIA13 tapes for high performance functions. The available MEDIA5, MEDIA9, or MEDIA11 tapes could then be used to their full capacity.

  Consider performance segmentation as a compromise solution. Performance segmentation increases the performance of data sets in the first twenty percent of the tape's capacity, but also uses the remaining capacity as a slower access segment. Average performance for the tape is increased at the expense of losing a percentage of the overall tape capacity. (You cannot determine which data sets reside in which segment.)

  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. Assume, for example, that your installation uses lower capacity tapes for ML2 and higher capacity tapes for backup. If you want to move only 100 GB of data from each recycled tape, calculate the percent that 100 GB represents of each of the two tape media. Then set RECYCLEPERCENT() to the calculated percent 100 GB represents of the backup media and set ML2RECYCLEPERCENT() to the calculated percent 100 GB represents of the smaller migration tapes. 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 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, the data class must request the appropriate media type for it to be successfully mounted.

• DFSMShsm recycle processing of 3592 Model E07 tapes can take significantly longer than with 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.
• 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.
• Consider using the Fast Subsequent Migration function to reduce the need to RECYCLE these high-capacity tapes.
• For a Sysplex environment, consider using the Common Recall Queue to optimize mounts of migration tapes.
• The 3592 Model E07 tape drive is used in 3590 emulation mode only; never 3490.