This exit allows you to get control during OPEN and RESTART processing of subsystem interface data sets. An indicator (passed to the exit in register 0) indicates either OPEN or RESTART processing; therefore, this exit can be used for either situation. Further, an indicator (passed in the parameter list pointed to by register 1) indicates the type of data set (SYSIN, SYSOUT, process SYSOUT, SPOOL BROWSE, or an internal reader type).

You can examine the data set characteristics and check them for validity, proper authority, or alter them.