IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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S 6.49 Data backup in a database
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: Administrators
As a rule, database systems cannot be backed up fully using backup programs
on the operating system level. In most cases, these programs simply act as a
link for writing the data on backup media. As far as most products are
concerned, backup of the database management system and information in the
database additionally requires the use of the database utility programs
integrated in the database management system.
The easiest and most reliable way of backing up a database is to perform a full
backup with the database shut down. In this process, all files belonging to the
database are saved on the storage medium. Usually however, this technique is
not feasible due to requirements of database availability or the volume of data
to be backed up.
One alternative to the full backup described above is online database backup.
In this case, the database is backed up while remaining in operation, i.e. it
does not need to be shut down. The disadvantages of this type of backup are
that inconsistencies cannot be ruled out explicitly, and that a full, offline
backup must nevertheless be available in the event of damage to the database,
to serve as a secure foundation for re-loading the online backups. For this
reason, online backups should only be performed if the database needs to
remain available on a continuous basis. Full, offline backups should
nevertheless be performed at reasonably regular intervals.
Partial database backups constitute another alternative. They should be made
use of whenever the data volume requiring backup is too large to allow a full
backup. This can result from situations in which the capacity of the backup
media has been exhausted or insufficient time is available for performing a
full backup.
If possible, all transactions between two full, offline backups should be
archived. In Oracle databases, for instance, the ARCHIVE mode can be
activated for this purpose. In Oracle, transactions are recorded in several log
files. These log files are written consecutively. Once all the files are full, the
first file is overwritten again. The ARCHIVE mode prepares backup copies of
the files before they are overwritten. This permits all transactions to be
reconstructed fully in the event of damage to the database. However, the
existence of a full database backup is also a prerequisite in this case. The
duration of such a recovery increases with the number of archived log files
which need to be restored.
A database backup policy needs to be prepared for backing up a database
system. Influencing factors in this policy are:
- Requirements of database availability
If a database needs to remain available round the clock on weekdays, for
example, full backups can only be performed on weekends, as the database
generally needs to be shut down for this purpose.
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IT-Baseline Protection Manual: Oktober 2000