Information held on the File Server can be defined in one of two categories:
- Data files - these are typically spreadsheet, configuration files, word processing files and user specific files created by application software.
- Application files - these are program files. Typically these files will have file extensions of EXE, OVR and DLL.
Responsibility for data security
The archive bitFile Attributes Archive Bit Attrib
Backup methodFull Backup Partial Backup
- Incremental: Only files whose archive bit is set ON will be copied to tape. Once the files are copied, the archive bit is set to off.
- Differential: Only files whose archive bit is set ON will be copied to tape. Once the files are copied, the archive bit is left unchanged.
- Selected files: Only files that are individually flagged will be copied to tape. The files are copied whether or not the archive bit is set. The archive bit may or may not be cleared from the files after the backup.
Tape rotation method
This ensures that:
- Different versions of backed up files can be maintained on different tapes.
- In the event of a tape failure during a restore, another recent tape is available.
- Certain tapes can be stored off site.
There are a number of different types of tape rotation methodologies. Listed below are some of the most commonly used systems.
Grandfather Father SonGrandfather Father Son
There are four tapes to be used only on Fridays - Friday1, Friday2, Friday3 and Friday 4. The Friday tapes are used depending on the week number within the month. For example, the Friday2 tape would be used on the second Friday of the month.
There are also twelve monthly tapes named January through December. These tapes are used on the last day of every month in preference to any other tapes.
Ten Tape Rotation
During the first four weeks the same tapes are used Monday to Thursday. At the end of each week a nominated end of week tape is used.
During the second four week cycle the tapes are brought forward one day and the weekly tapes (shaded) are brought forward. The table below illustrates the tapes numbers and the usage sequence.
Ten Tape Rotation
These tapes are rotated with the other tapes in the cycle so that there are always a number of tapes stored off site in a secure location.
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