Oracle7 Server Administrator's Guide

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Creating a Backup Strategy

Before you create an Oracle database, decide how you plan to protect the database against potential failures. Answer the following questions before developing your backup strategy:

Backup Strategies in NOARCHIVELOG Mode

If a database is operated in NOARCHIVELOG mode, filled groups of online redo log files are not being archived. Therefore, the only protection against a disk failure is the most recent full backup of the database.

Plan to take full backups regularly, according to the amount of work that you can afford to lose. For example, if you can afford to lose the amount of work accomplished in one week, make a full offline backup once per week. If you can afford to lose only a day's work, make a full offline backup every day. For large databases with a high amount of activity, it is usually unacceptable to lose work. Therefore, the database should be operated in ARCHIVELOG mode, and the appropriate backup strategies should be used.

Whenever you alter the physical structure of a database operating in NOARCHIVELOG mode, immediately take a full database backup. An immediate full backup protects the new structure of the database not reflected in the previous full backup.

Backup Strategies in ARCHIVELOG Mode

If a database is operating in ARCHIVELOG mode, filled groups of online redo log files are being archived. Therefore, the archived redo log coupled with the online redo log and datafile backups can protect the database from a disk failure, providing for complete recovery from a disk failure to the instant that the failure occurred (or, to the desired past point-in-time). Following are common backup strategies for a database operating in ARCHIVELOG mode:

Note: When you perform this initial full backup, make sure that the database is in ARCHIVELOG mode first. Otherwise, the backed up database files will contain the NOARCHIVELOG mode setting.

Warning: If the control file does not contain the name of a datafile, and you have no backup of that datafile, you cannot recover the file if it is lost. Also, do not use operating system utilities to backup the control file in ARCHIVELOG mode, unless you are performing a full, offline backup.


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