On an extended address volume, partial release processing performed by the system for a non-striped VSAM data set ensures that point where unused space is to be released from is on a multi-cylinder unit boundary. Additionally, for a striped VSAM data set the system ensures that the point where unused space is to be released from for all stripes results in stripes of the same size. In either case, the system cannot release some or all of the unused space from the end of the data set.

If you allocate space for a data set in a unit smaller than one cylinder, VSAM allocates space in tracks when defining the data set. For data sets less than 1 cylinder in size, it is best to specify the maximum number of tracks required in the primary allocation for the data component, 1 track for the sequence set index (which should not be imbedded), and no secondary allocation for either data or index.

VSAM checks the smaller of primary and secondary space values against the specified device's cylinder size. If the smaller quantity is greater than or equal to the device's cylinder size, the control area is set equal to the cylinder size. If the smaller quantity is less than the device's cylinder size, the size of the control area is set equal to the smaller space quantity. The minimum control area size is one track. See Optimizing Control Area Size for information about creating small control areas.