Maximum VSAM Data Set Size

A VSAM data set is limited to 4 GB across all volumes unless Extended Addressability is specified in the SMS data class definition. System requirements restrict the number of volumes that can be used for one data set to 59.

Using extended addressability, the size limit for a VSAM data set is determined by either:

Control interval size multiplied by 4 GB
The volume size multiplied by 59.

A control interval size of 4 KB yields a maximum data set size of 16 TB, while a control interval size of 32 KB yields a maximum data set size of 128 TB. A control interval size of 4 KB is preferred by many applications for performance reasons. No increase in processing time is expected for extended format data sets that grow beyond 4 GB. To use extended addressability, the data set must be:

SMS-managed
Defined as extended format.