ICSF calls the service exits in cross memory mode after a space switch PC. The exits run in the ICSF address space, which is the primary address space. The exits need to address parameters in the caller's address space, which is the secondary address space. In general, user-passed parameters, including the parameter list itself, are in the secondary address space. An exit that is running in access register (AR) mode using an ALET of 1 can access these parameters. For information about cross memory mode and AR mode, see z/OS MVS Programming: Extended Addressability Guide.