Guidelines for allocating large format data sets:

• To allocate a large format data set, specify LARGE for the DSNTYPE value on the JCL DD statement, the access method services ALLOCATE command, the TSO/E ALLOCATE command, or SVC 99 (dynamic allocation).
• If no DSNTYPE is specified on the DD statement, ALLOCATE command or dynamic allocation, and DSORG isn't set to anything other than PS or PSU, then the Data Class can provide the LARGE value as a default.
• DSORG must be set to DSORG=PS or DSORG=PSU, or omitted.

Restrictions: The following types of data sets cannot be allocated as large format data sets:

• PDS, PDSE, and direct data sets
• Virtual I/O data sets, password data sets, and system dump data sets.

The following do not support large format data sets:

• The BDAM access method.
• TSO COPY command, part of the TSO Data Utilities product.