EDGTVEXT ensures that DFSMSrmm is in use on your system before continuing with DFSMSrmm processing. If DFSMSrmm is not in use, EDGTVEXT sets return code zero and returns to the caller. If DFSMSrmm is in use or should be in use, EDGTVEXT calls EDGDFHSM to process the volumes passed to it in the ARCTVEXT parameter list.