DFSMShsm loops through the entries for the data sets on the volume
and backs up all those data sets that are eligible. An eligible data
set is one that:
- Has the management class ADMIN OR USER COMMAND BACKUP attribute
value of ADMIN or BOTH
- Has the management class AUTO BACKUP attribute value of Y
- Has eligibility, as determined by the data-set-changed indicator,
as follows:
- If the data-set-changed indicator is off and SETSYS INCREMENTALBACKUP(ORIGINAL)
is specified, DFSMShsm backs up the data set if no prior backup version
exists.
- If the data-set-changed indicator is on and DFSMShsm can determine
a last backup date, DFSMShsm backs up the data set if the number of
days since the last backup date equals or exceeds the value specified
with the management class BACKUP FREQUENCY attribute.
- If the data-set-changed indicator is on but DFSMShsm cannot determine
a last backup date (indicating a new data set), DFSMShsm backs up
the data set.
- If the data-set-changed indicator is on and the data set resides
on a volume in a storage group that is defined with the GUARANTEED
BACKUP FREQUENCY attribute, DFSMShsm backs up the data set if the
number of days since the last backup date equals or exceeds the value
that is specified by GUARANTEED BACKUP FREQUENCY days.
If the data set is eligible for backup and the exit is enabled,
DFSMShsm passes control to the data set backup exit (ARCBDEXT).
For those data sets that are backed up, DFSMShsm invalidates the
oldest excess versions that exceed the limit specified with the NUMBER
OF BACKUP VERSIONS (DATA SET EXISTS) management class attribute.