Partial Release

Partial release is used to release unused space from the end of an extended format data set and is specified through SMS management class or by the JCL RLSE subparameter. For data sets whose ending high used RBA is in track managed space, all space after the high used RBA is released on a CA boundary up to the high allocated RBA. If the high used RBA is not on a CA boundary, the high used amount is rounded to the next CA boundary. For data sets whose ending high used RBA is in cylinder-managed space, all space after the high used RBA is released on an MCU boundary up to the high allocated RBA. If the high used RBA is not on an MCU boundary, the high used amount is rounded to the next MCU boundary. Partial release restrictions include:

Partial release processing is supported only for extended format data sets.
Only the data component of the VSAM cluster is eligible for partial release.
Alternate indexes opened for path or upgrade processing are not eligible for partial release. The data component of an alternate index when opened as cluster could be eligible for partial release.
Partial release processing is not supported for temporary close.
Partial release processing is not supported for data sets defined with guaranteed space.

For extended format data sets, partial release can release unused space across multiple volumes, from the high used RBA (or next CA/MCU boundary) to the high allocated RBA. Partial release requires that the primary volumes in the data set be in ascending order by RBA. For example, the first volume could have RBAs 1 to 1000, the next 1001 to 2000, and so on. If the primary volumes appear out of order, partial release issues an error message and releases no space.

VSAM CLOSE will request partial release processing only if:

Partial release was specified through SMS management class or by the JCL SPACE=(,,RLSE) parameter on the DD statement.
The data set is defined as extended format.
The data set was opened for OUTPUT processing.
This is the last ACB closing for the data set (this includes all closes in the current address space, other address spaces in the system, and other systems).