z/VSE

This field is a fullword and always contains zeros. It is included to maintain compatibility with the Exit Parameter List in the z/VM and z/OS environments.

z/VM and z/OS

The DCB pointer is a fullword that contains the address of the Data Control Block.

When an exit is invoked with an OPEN request, the data set referred to by the DCB is not open, and the contents of the DCB might not be complete.

When an exit is invoked with a PROCESS request, the exit might use the DCB to obtain additional information about the data set or member being used. For example, on z/OS, the exit can obtain user information from a PDS or PDSE directory by using the BLDL system macro.