What is DFSMShsm?

DFSMShsm (Data Facility Storage Management Subsystem Hierarchical Storage Manager) is an IBM mainframe software product used for automated hierarchical storage management. It automatically migrates infrequently used data from expensive, high-performance storage devices (like disk) to less expensive, lower-performance storage devices (like tape). It also automatically recalls data when it is accessed. This helps optimize storage costs and performance.