DFSMSdss releases allocated, but unused, space from sequential data sets, PDSs, PDSEs, and extended-format VSAM data sets using either volume or catalog filtering. DFSMSdss allows you to perform the following tasks:

• Release space only if the unused space is larger than the number of tracks that you specify.
• Release unused space in system data sets.
• Retain a specified secondary space allocation, leaving space in order to add records to the data set after DFSMSdss releases the unused space.