Recommendation: Implement the changes in two steps. Define the DFSMSrmm system at this time as described in Defining DFSMSrmm to z/OS. Then you can add the name of the subsystem interface as described in Step 22: Initializing the DFSMSrmm subsystem and tape recording. If you make only this first change at this time, you can choose whether to start the DFSMSrmm procedure and choose a time to best suit your particular situation. If you implement both changes at once, DFSMSrmm rejects all tape mounts until the subsystem procedure is active or you use the EDGRESET utility to disable the interface.