A BCS is limited to 4 GB unless you define it as an extended format BCS, which means it can use extended addressability. Using extended addressability, the size limit for a BCS is determined by the control interval size multiplied by 4 GB. For example, 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. No increase in processing time is expected for extended format data sets that grow beyond 4 GB. To use extended addressability, the BCS must be SMS managed and defined as extended format.

You can specify extended format for a BCS using SMS data class DSNTYPE=EXT parameter and subparameters R (meaning required) or P (meaning preferred) on the ISMF DATA CLASS DEFINE/ALTER panel. Use R to ensure the BCS is extended. The Extended Addressability value must be set to Y (Yes).

The only extended format option available for a BCS is extended addressable. This means that BCSs cannot be compressed or striped.