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.
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 MEDIA5 or MEDIA9 overall
tape capacity. (You cannot determine which data sets reside in which
segment.)
DFSMShsm recycle processing of 3592 Model E05 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.
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 MEDIA7 tape
for ML2 and MEDIA5 tape for backup. If the EFMT1 format is used and
you would like no more than 6 GB of data to be moved when an ML2 tape
is recycled, set ML2RECYCLEPERCENT(10) because the MEDIA7 can hold
60 GB of data in EFMT1. If your installation uses full capacity for
backup tapes and you want no more than 6 GB of data to be moved when
a backup tape is recycled, set RECYCLEPERCENT(2) because a MEDIA5
tape can hold 300 GB of data in EFMT1. 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, the data class must request
the appropriate media type for it to be successfully mounted.