The MVS router parameter list is generated when the RACROUTE macro is issued, and describes the security processing request by providing the request type. If the router exit routine exists, the router passes the parameter list to this exit. (If it does not exist, and if RACF is active, the router passes the parameter list to the RACF router.)
You can map the MVS router parameter list using the ICHSAFP macro. Its format is shown in the MVS/ESA Diagnosis: Data Areas manual.