ACT DFHSM Backup Data Sets

DFHSM can automatically create backup copies of data sets according to installation-defined rules. System Managed Storage (SMS) management class definitions can also be used to specify backup frequency and the number of backup versions that are to be kept. When DFHSM performs automatic backup of data sets, the Backup Control Data Set (BCDS) is updated with information about each backup copy or backup version created on backup volumes managed by DFHSM.
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DFHSM can automatically create backup copies of data sets according to installation-defined rules. System Managed Storage (SMS) management class definitions can also be used to specify backup frequency and the number of backup versions that are to be kept. When DFHSM performs automatic backup of data sets, the Backup Control Data Set (BCDS) is updated with information about each backup copy or backup version created on backup volumes managed by DFHSM.
The pyramid forms a useful analogy for considering the potential amount of data for backup versions. Consider this pattern of usage for typical TSO users and the backup rules associated with a "STANDARD" management class:
  • 25 percent of a given user's data sets are changed each day.
  • An HSM rule states data sets are only to be backed up if they have been changed.
  • A management class definition states that five backup versions are to be kept.
Thus, for an active data set that is changed every day, the BCDS will contain information for five backup versions of this data set in our hypothetical example above.
Expanding this scenario to an entire DASD complex, there might be the following kind of relationship in terms of the relative number of data sets:
/\ / \ / \ / \ / \ / Primary \ /____________\ / \ / \ / \ / Backup \ / Versions \ / \ / \ /____________________________\
Information on backup versions of data sets is available from the
MICS Space Analyzer Option
HSM product via the
MICS Space Collector Option
(VCC). VCC can optionally collect basic accounting and capacity planning information about backup versions of data sets by serving as a "driver" for the collection of data from the BCDS.
Using the
MICS Space Analyzer Option
HSM product, you can establish different pricing for storage occupied for backup versions. Because the backup versions typically exist on high-density tape cartridges, the relative charge for storage occupancy (that is, amount of space times duration or megabyte days) is undoubtedly less for backup versions than for primary DASD storage occupancy. An example follows:
/\ / \ / \ / \ / \ / \ / \ / \ / $1.25 \ / per \ / megabyte day \ /______________________\ / \ / $0.05 \ / per \ / megabyte day \ /________________________________\
See DASD Accounting Features for more information about this subject.