When you start DFSMShsm, a subset of DFSMShsm control parameters is established by default. You can override DFSMShsm defaults by specifying one or more SETSYS commands in the ARCCMDxx PARMLIB member used when you start DFSMShsm. You can issue the SETSYS command with specific parameter values after DFSMShsm is started to change the current defaults. The changed values remain in effect until you restart DFSMShsm. For an example of how to set up the ARCCMDxx PARMLIB member, see the DFSMShsm installation verification procedure in z/OS V2R1 Program Directory .
If you do not specify the SETSYS command, DFSMShsm does not do any automatic space management, backup, or dump. Therefore, if you want to take advantage of the automatic functions of DFSMShsm, use the SETSYS command.
Do not confuse DFSMShsm defaults with the SETSYS command defaults. Except for certain values, there are no SETSYS command defaults. A SETSYS command does not have required parameters, so unless you indicate a specific parameter value for the SETSYS command, the DFSMShsm control parameter is the default. An exception to this is the CDSVERSIONBACKUP parameter.