Request compression at the data set level
You request compression at the data set level by defining a data class with the compaction options ZR (zEDC Required) or ZP (zEDC Preferred).
The compaction option on the DFSMS Data Class Define panel is as follows:
- Compaction
- Specifies whether the data set is to be
compressed format. You can compress data that is being written to an extended format data set or to
a PDSE. This field is ignored for DASD data sets if the data set name type is not EXT or LIBRARY.
You can compress data when it is being written to tape. A compressed data set cannot reside on the
same tape cartridge as a data set that is not compressed.
The possible values are:
- Y
- Extended format or PDSE data sets are compressed and tape volumes are compacted. The type of DASD compression depends on the COMPRESS option in parmlib member IGDSMSxx. Tape volumes are compacted unless compaction is overridden by the user through JCL/dynamic allocation.
- N
- Data sets are not compressed. Tape volumes are not compacted, unless compaction is requested by the user through JCL/dynamic allocation.
- T
- Extended format data sets are compressed using tailored dictionaries. This overrides the COMPRESS option in parmlib member IGDSMSxx.
- G
- Extended format data sets are compressed using generic dictionaries. This overrides the COMPRESS option in parmlib member IGDSMSxx.
- ZR
- Indicates
zEDC Required
, meaning that the system should fail the allocation request if the zEDC function is not supported by the system, or if the minimum allocation amount requirement is not met. - ZP
- Indicates
zEDC Preferred
, meaning that the system should not fail the allocation request, but rather create either a tailored compressed data set if the zEDC function is not supported by the system, or a non-compressed extended format data set if the minimum allocation amount requirement is not met. - blank
- Data sets are not compressed. Tape volumes might be compacted depending on what was specified by the user on JCL/dynamic allocation, the installation with the COMPACT option in parmlib member DEVSUPxx, or the allocated hardware model. This is the default.
T, G, ZR, and ZP override the compression option set in the IGDSMSxx PARMLIB member, and let you select the type of compression on a data set level. Current® users of generic compression can move to using tailored or zEDC compression one data set at a time, as new data sets are created.