The linkage is created as follows:

• For non-IBM modules, or modules written in languages other than PL/X, the CALL statement must generate a V-type constant (VCON) with the module name of a stub routine for the requested service. The module names are defined as part of the callable services interface described in Callable services descriptions. The VCON can be resolved by link-editing the control section (CSECT) with the stub routines provided as part of MVS™'s system authorization facility (SAF). There is a stub for each service.
• The linkage loads a function code indicating the service requested and calls the callable services router. The function codes that can be used are described in z/OS Security Server RACF Data Areas.
• The callable services router calls an installation exit (IRRSXT00 for 31 bit callers or IRRSXT0X for 64 bit callers).
• The RACF® router invokes the requested service routine based on the function code.
• The service routine provides the requested function and returns to the SAF callable services router.
• The SAF callable services router calls the installation exit IRRSXT00 or IRRSXT0X a second time, sets the SAF return code, and returns to the caller.