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zEDC and HSM - A Winning Combination

By Anthony Giorgio posted Thu April 02, 2020 03:45 PM

DFSMShsm users often ask how they can reduce the MIPS, elapsed time and storage required to archive unreferenced data.  There is now a simple answer - zEDC.

As unreferenced data ages, it is cost beneficial to move that data to a compressed format on offline storage.  This is accomplished through DFSMShsm space management processing.  Clients have indicated that space management processing is one of the largest consumers of MIPS and storage resources in their environments.  This is only exacerbated as environments grow larger and space management  windows encroach on, or even contribute to, the 4-hour rolling MIPS average.

imageThe system resources required to archive data to offline storage can now be significantly reduced through the use of zEDC.  When migrating data to ML1 disk, zEDC can replace standard DFSMShsm software compression.  IBM testing has shown that zEDC can reduce ML1 migration MIPS by as much as 80%, elapsed time by as much as 15% and ML1 disk space by as much as 58%. 


Before the introduction of zEDC, using host based compression when migrating directly to tape was not recommended because of the MIPS required to compress the data.  The same compression results could be achieved through tape control unit compression without consuming MIPS.

imageWith zEDC, a significant savings can now be achieved by first compressing the data because of the significant reduction in the number of blocks that are processed by DFSMShsm.  Besides reducing the MIPS consumption by up to 15%, elapsed time may be reduced by as much as 25%.  Also, since zEDC can achieve a higher compression ratio than a tape control unit, virtual tape space may be reduced by as much as 37%.  The reduction in the number of blocks written to tape also reduces the overall MIPS and elapsed time required for RECYCLE processing.

(Be sure to apply APAR OA48394 before enabling zEDC for DFSMShsm data written directly to tape.  This development APAR provides an algorithmic improvement that provides these MIPS and elapsed time improvements that will only be achieved after this APAR has been applied).

Recall also offers MIPS and elapsed time improvements.  Recalling zEDC compressed ML1 data has shown a 69% reduction in MIPS.  Recalling zEDC compressed data from ML2 virtual tape has shown a reduction of 11% in MIPS and 32% in elapsed time. 

Similar results can be achieved when using zEDC for data set level backup and recovery.

With zEDC and z/OS V2R1 or higher in your environment, enable DFSMShsm usage by simply adding the SETSYS ZCOMPRESS(ALL) setting to your DFSMShsm PARMLIB member and watch the immediate improvement!


Disclaimer: All stated improvements are based on measurements completed in a controlled environment.  Results may vary by customer based on individual workload, configuration and software levels.

Note: For full volume dump processing, while enabling zEDC compression will result in improved compression, it will also increase MIPS usage if you are not already compressing the data before writing to tape.  The ZCOMPRESS option in the DEFINE DUMPCLASS command enables zEDC for dump processing.  The default is NO.