A few tips on how to handle problems with IBM's DFSMSHSM, just called HSM hereafter. HSM is a backup and recovery product, and also a migrate and retrieve product. It works on the concept of a storage hierarchy, where commonly used data is kept on fast access disk, data which has not been referenced for a while is archived off to compressed disk, then eventually to slower access tape. HSM is policy based, it uses DFSMS constructs called management classes to decide, almost on a file by file basis, how long a file is kept at each level in the storage hierarchy, and how often that file gets backed up. HSM can also be used to control data retention, it can delete unused data once a preset time is reached.
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