Consolidating free space and extents on volumes

Because of the nature of allocation algorithms and the frequent creation, extension, and deletion of data sets, free space on DASD volumes becomes fragmented. This results in:

Inefficient use of DASD storage space
An increase in space-related abends (abnormal endings)
Performance degradation caused by excessive DASD arm movement
An increase in the time required for functions that are related to direct access device space management (DADSM).

With the DEFRAG command, you can consolidate the free space on volumes and avoid this problem. The DEFRAG command relocates data set extents on a DASD volume to reduce or eliminate freespace fragmentation, and prints a report about free space and other volume statistics. Also, you can specify which data sets, if any, are to be excluded from data-set-extent relocation. Data set extents are not combined as a result of DEFRAG processing.

Note: Data set extents will not be moved between the track-managed space and cylinder-managed space of an extended address volume during DEFRAG processing.