In a node backup to magnetic tape cartridge, the save file is automatically duplicated if the node backup archive concerned was assigned a shadow archive. The automatic duplication mechanism must be activated by default (see the OPERATION-CONTROL operand of the HSMS statement BACKUP-NODE-FILES).
The save file is copied into the assigned shadow archive at the end of the backup run. The copy in the shadow archive is given the same save version ID and save file ID as the original, i.e. it receives the same time stamp.
The directory file of the shadow archive can differ from that of the associated node backup archive because not all backups are copied to the shadow archive (backups to disk, backups for which SHADOW-COPY=*INHIBITED is specified, a new shadow archive can be linked to a non-empty backup archive).
If a save file in a node backup archive is to be extended, the automatic duplication mechanism also attempts to extend the save file with the same SFID in the assigned shadow archive. If this save file does not exist, duplication is not carried out.
The automatic duplication mechanism enables the precautionary measures against data loss to be adapted to the requirements and to the storage capacity of a computer center:
Maximum data security, with very high costs with regard to tape consumption and high costs with regard to backup times:
Each system backup archive is assigned a shadow archive.
All backups are performed with the specification SHADOW-COPY=*ALLOWED and the archive attribute SHADOW-COPY=*ALLOWED-AND-NEW-SFID.
Result:
Every backup on S2 is automatically copied to the shadow archive and the tape copy is then immediately placed in a secure storage location.
Maximum data security, with high costs with regard to tape consumption and backup times:
Each system backup archive is assigned a shadow archive.
All backups are performed with the specification SHADOW-COPY=*ALLOWED.
Result:
Every backup on S2 is automatically copied into the shadow archive.
Medium data security, with average costs for tape consumption and backup times:
Each system backup archive is assigned a shadow archive.
All weekly full backups are performed with the specification SHADOW-COPY= *ALLOWED.
The incremental backups in between are performed with the specification SHADOW-COPY=*INHIBITED.
Result:
Only the weekly full backups on S2 are copied to the shadow archive.
Low data security, with lower costs for tape consumption and backup times:
No shadow archives are assigned to the system backup archives.
Result:
The automatic duplication mechanism is not used.