You are offered the option of being able to release data sets, and the volumes the data sets reside on when your task is no longer using them. If you are not sharing data sets, these data sets would otherwise remain unavailable for use by other tasks until the job step that opened them ends.

There are two ways to code the CLOSE macro that can result in releasing a data set and the volume on which it resides at the time the data set is closed:

1. For non-VSAM data sets, you can code the following with the FREE=CLOSE parameter:

      CLOSE   (DCB1,DISP) or
      CLOSE   (DCB1,REWIND)

   See z/OS MVS JCL Reference for information about using and coding the FREE=CLOSE parameter of the DD statement.

2. If you do not code FREE=CLOSE on the DD statement, you can code:

      CLOSE   (DCB1,FREE)

In either case, tape data sets and volumes are freed for use by another job step. Data sets on direct access storage devices are freed and the volumes on which they reside are freed if no other data sets on the volume are open. For additional information on volume disposition and coding restrictions on the CLOSE macro, see z/OS MVS JCL User's Guide.

If you issue a CLOSE macro with the TYPE=T parameter, the system does not release the data set or volume. They can be released using a subsequent CLOSE without TYPE=T or by the unallocation of the data set.