IMS Standard User Exit Parameter List

Many of the IMS user exit routines use a standard user exit interface. This interface allows the exit routines to use callable services to access IMS blocks. At the same time, this interface creates a clearly differentiated programming interface (CDPI) between IMS and the exit routine. Part of the interface consists of a standard user exit parameter list. The list contains items such as a pointer to a version number and a pointer to a function-specific parameter list. All standard user exit parameter lists that have the same version number will contain the same parameters. If a new parameter is added, it is added to the end of the parameter list and the version number is increased by one.

If an exit routine is written to use a parameter that was added in a later version, and the exit routine can execute in an environment in which earlier versions of the parameter list could be received, the exit routine should check the version of the parameter list it received to ensure that the data is available to the exit routine.