You can use the SET SMS or SETSMS MVS command to change SMS parameters. Use the SET SMS command to initialize SMS parameters from PARMLIB member IGDSMSxx and start SMS (or restart SMS if it was already active). Use the SETSMS command when SMS is active (running) to change a subset of SMS parameters by entering them from the console without changing IGDSMSxx.
For descriptions of SET SMS and SETSMS, see z/OS MVS System Commands.