Application program request support

Application calls are passed to IMS from the language interface module that you bind with the application program. The language interface branches to the appropriate IMS program request handler passing the application program call parameter list.

For calls directed to external subsystems, the language interface must also pass an external subsystem parameter list which it constructs. The purpose of this parameter list is to pass the LIT (language interface token) for the external subsystem to which the call is directed. IMS routes the application call to the external subsystem whose LIT value matches the LIT value passed on the call.

IMS passes both the call parameter list and the external subsystem parameter list to the Normal Call exit routine for the intended external subsystem. The first word of the external subsystem parameter list contains the address of a 4-byte field containing the LIT value in character format, left justified and padded on the right with blanks. IMS prescribes only the first word in the external subsystem parameter list (address of the LIT). The parameter list can be extended to provide external subsystem-dependent information to the Normal Call exit routine.