PDS Compression › JCL — PDS Compression › COMPRESS Command

COMPRESS Command

The COMPRESS command must be used to explicitly compress individual datasets.

The COMPRESS command syntax is:

COMPRESS SIMULATE,DSNAME=,VOLUME=,THRESHOLD=,EMPTY,USE,SHRINK,CONVERT,

ALLOCATE=,SPACE=,RESERVE,PASSWORD

DSNAME=

This parameter designates the name of the PDS to be compressed.

VOLUME=

This parameter must be supplied when the PDS is not cataloged. If the PDS is SMS managed, the USE parameter must also be specified. Otherwise, the data set will be bypassed.

SPACE=

Use this parameter when you want to provide absolute values (rather than percentages) for the new space allocation of a PDS.

• When processing in implicit (SCAN) mode, using percentage values for calculating the reallocation amounts permits efficient processing of numerous datasets. However, when specifying an explicitly named PDS (COMPRESS), the desired reallocation amounts are often known, and can be supplied directly using this parameter. SPACE= can be used only with explicit processing.
• To request actual space reallocation quantities, specify SPACE= in conjunction with the ALLOCATE= parameter. When thus combined, the SPACE= parameter supplies the allocation type, while the ALLOCATE= parameter supplies the allocation quantities. For example, specifying means to reallocate the PDS with 30 primary tracks and 10 secondary tracks, and a block directory

  SPACE=TRK,ALLOCATE=(30,10,5)
  

• If SPACE= is specified without the ALLOCATE= parameter, the data set will be reallocated using the new allocation type. For example, specifying will convert the original allocation to cylinders with the CONTIG attribute.

  SPACE=CYLCTG
  

• If SPACE= is specified, the USE, SHRINK, CONVERT, EMPTY, and THRESHOLD parameters are ignored.

Note: The use of the SPACE= parameter will force the compression of empty datasets, whether the EMPTY parameter is specified or not.

Specify this parameter with one of the following literal values:

Note: For any type of block allocation, the block size is obtained from the data set's format-1 DSCB. If the block size is 0 (or greater than the maximum block size for the device), the block size is assumed to be the maximum for the new device; therefore the new allocation will be the same number of tracks as the number of blocks specified.