Introduction to DFSMShsm

DFSMShsm is a licensed program that automatically performs space management and availability management in a storage device hierarchy. DFSMShsm makes sure that space is available on your Direct Access Storage Device (DASD) volumes so that you can extend your old data sets and allocate new ones. DFSMShsm also makes sure that backup copies of your data sets are always available if your working copies are lost or corrupted.

DFSMShsm terminology includes the following:
Space management
Functions that ensure space is available for extending and allocating data sets.
Availability management
Functions that make backup copies available.
Authorized user
An authorized user is someone whom the computing center has authorized to issue all of the DFSMShsm commands. Authorized users can issue commands that affect other users data sets.
Unauthorized user
An unauthorized user is someone who can issue only a limited subset of the DFSMShsm commands, called the unauthorized commands. Unauthorized users can affect only their own data sets.