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DFSMShsm is an automated hierarchical storage manager and productivity tool designed to support Availability Management, Space Management, and Disaster Recovery.
- The Storage Hierarchy:
- A storage device hierarchy consists of a set of storage devices that have differing costs for storing data, differing amounts of data stored, and differing speeds for accessing the data. Storage devices at the lower level typically provide lower cost per byte storage and may have slower access time. These devices may be disk or tape.
- Availability Management:
- Availability management is the process that helps maintain a backup copy of data sets which can be easily recovered if the original copy is damaged or accidentally deleted.
DFSMShsm can automatically make backup copies of changed data sets and copies complete volumes (dumps) according to a definable schedule. DFSMShsm can also create a point-in-time copy of a set of volumes using the Flashcopy™ process and automatically move those copies to tape.
- Space Management:
- Space management is a process that monitors usage to maintain enough space on user volumes for new and active data.
- DFSMShsm uses a three-level storage device hierarchy for space management:
- Level 0 contains data directly accessible to the end user or program.
- Level 1 is disk containing data sets that DFSMShsm has moved from level 0 volumes.
- Level 2 is tape containing data sets that DFSMShsm has moved from level 1 or level 0 volumes.
- DFSMShsm can automatically move (migrates and recalls) data sets, which have not been referenced within a specified time, to lower cost devices. A migrated data set is one that has been moved to a Level 1 or Level 2 volume, DASD or tape, in a special space saving form on the volume.
- DFSMShsm can automatically delete data sets that have passed their expiration dates.
- DFSMShsm can automatically free over-allocated space
- Disaster recovery:
- Disaster recovery is provided by ABARS (Aggregate Backup And Recovery Support).
Aggregate backup is a command-driven function that can back up a user-defined group (called an aggregate group) of data sets for recovery at another computer site or at the same site. Aggregate recovery is the command-driven function that recovers the data sets that were previously backed up by aggregate backup.
- List, report, query, audit:
- DFSMShsm can manage backed up, dumped, and migrated volumes and data sets. It can maintain an inventory and provides features so users may find information about their own volumes and data sets through LIST, REPORT, QUERY, and AUDIT functions.
DFSMShsm may be set up to run automatically, manually, or from user programs.
DFSMShsm may manage data based on the policies defined in SMS Management Classes and Storage Groups.
IBM recently announced new, higher capacity cartridges for the IBM System Storage TS1120 tape subsystem. These new cartridges have a physical capacity of around 700 GB and a logical capacity of around 2 terabytes when compressed at 3:1. DFSMShsm can use these high capacity tapes for all tape related functions.
IBM also recently announced tape hardware encryption for the TS1120 drive. Since the data encryption is done at the drive level, DFSMShsm's backup, migration, dump and ABARS tapes can be protected without compromising the time required to write data to tape. See 1.0 Encryption-capable TS1120 tape drive for implementation details.
The J70 and the C06 tape controllers now have a high speed search capability for finding data strings on tape. DFSMShsm exploits this new capability when examining a DFSMShsm created tape with the DFSMShsm Audit function, dramatically lowering execution times and CPU usage.
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