Automatic backup example
Table 1 shows the conditions that pertain to a group
of data sets at the beginning of automatic backup. See Example management classes for
a description of the management classes for these data sets. The names
of the data sets are not precisely as the system would generate them.
They have been shortened and modified for convenience in using them
for illustrations.
Note: The management class name has been
used as the high-order qualifier for the data set names for your convenience
in comparing the conditions of the data sets with the attributes specified
in the management classes. This is purely for educational purposes.
You are not required to use the management class name as any qualifier
in the data set name for SMS-managed data sets.
| Data set name | Number of existing backups | Last backup (days) | Data set changed indicator | Data set was backed up |
|---|---|---|---|---|
| GDSMC.G3.V1 | 0 | 0 | Yes | Yes |
| GDSMC.G3.V2 | 1 | 1 | Yes | Yes |
| LARGEMC.G4.E1 | 4 | 3 | Yes | Yes |
| LARGEMC.G4.E2 | 4 | 2 | No | No |
| NOMIGMC.G4.G1 | 0 | 4 | Yes | No |
| STANDMC.G4.H1 | 3 | 2 | Yes | No |
As DFSMShsm processes each of the data sets, the following occurs:
- Data set GDSMC.G3.V1 is backed up because the data-set-changed indicator is on and no backup version exists.
- Data set GDSMC.G3.V2 is backed up because the data-set-changed indicator is on and the data set has met the BACKUP FREQUENCY specified in management class GDSMC. However, because a backup version of the data set already exists and the new backup copy exceeds NUMBER OF BACKUPS (DATA SET EXISTS) specified in management class GDSMC, DFSMShsm invalidates the old backup version.
- Data set LARGEMC.G4.E1 is backed up for the same reason as for GDSMC.G3.V2. Note, however, that the days since last backup exceeds the value specified for BACKUP FREQUENCY in management class LARGEMC. This happened because the data set was last backed up on Friday. (Remember, the example system is running on a Monday.) Whether the data set changed on Friday (after backup ran), Saturday, Sunday, or Monday, it could not be backed up until Monday. This data set also causes a roll-off of the existing backup version.
- Data set LARGEMC.G4.E2 is not backed up because the data-set-changed indicator is set off.
- Data set NOMIGMC.G4.G1 is not backed up even though the data-set-changed indicator is on and the last backup meets the BACKUP FREQUENCY attribute in management class NOMIGMC. The data set is not backed up because the AUTO BACKUP attribute value is N in management class NOMIGMC.
- Data set STANDMC.G4.H1 is not backed up because, even though the data-set-changed indicator is on, the last backup days value does not meet the BACKUP FREQUENCY specified in management class STANDMC.