Improving device performance with hardware compaction algorithms

Data compaction improves tape processing performance because tapes can hold more data when the data is compacted, thus reducing the number of tape mounts when tape media is fully utilized. DFSMShsm provides software compaction, but that compaction depends on processor resources to compact data.

Data compaction can also be implemented at the device level, allowing the hardware, and not the main processor, to compact data. These kinds of compaction algorithms are available on all 3490 and 3590-1 devices and can be installed on 3480 devices.

Note: A 3480 device with improved data-recording capability (IDRC) is referred as a 3480X and the tape that is compacted with a 3480X device as a 3480X tape.

The cartridge-type device with the compaction algorithm function compacts data whenever data is moving to tape, whether it is from a level 0 volume, DASD migration volume, or another tape. When data is subsequently read from a cartridge-type device, data is decompacted before DFSMShsm receives the data.