Extended-Format Data Sets

You can allocate both sequential and VSAM data sets in extended format on a system-managed DASD. The DASD is attached to a controller that supports Extended Platform.

An extended-format data set supports the following formats:

Compression, which reduces the space for storing data and improves I/O, caching, and buffering performance.
Data striping, which distributes data for one data set across multiple SMS-managed DASD volumes, which improves I/O performance and reduces the batch window. For example, a data set with 28 stripes is distributed across 28 volumes.
Extended-addressability, which enables you to create a VSAM data set that is larger than 4 GB.

Extended-format VSAM data sets allow you to release partial space and to use system-managed buffering for VSAM batch programs. You can select whether to use the primary or secondary space amount when extending VSAM data sets to multiple volumes.

Related reading: For more information on extended-format data sets, see z/OS DFSMS Using Data Sets.