Oracle Tips Donald K. Burleson

Backup Methodologies

NT or UNIX System Backup

NT or UNIX system backups (such as TAR or DUMP) should be taken on at least a weekly basis. The Oracle database(s) can either be shut down  or a hot backup may be used and a full backup taken.

t should be remembered that recovery is only to the time the backup was taken. All control, data, and archive logs must be backed up at the same time. The data from the backup forward is recovered from the archive and on-line redo logs. Therefore, even though redo logs are backed up, they should not be restored unless the on-line redo logs have been lost. Always recover using an on-line redo log and the most current control file if possible. If you must use a control file restored from the backup, use the USING BACKUP CONTROLFILE option of the recover command..

Import/Export

As a minimum, export after large table loads for major tables.

All export procedures should be logged so that they can be reviewed. Some data corruption problems, such as unreadable characters in a record, will only be caught by the export process.

Archive Logging

Archive logging is strongly suggested for all Oracle databases.

Archive logging is automatic; it may consume disk resources in a highly active environment. If recovery is required, the system will ask for the archive logs it needs and perform recovery from them. Archive logs allow point-in-time recovery. To use hot backup, archive logging is required. Some sites switch on archive logging during a hot backup and then switch it off; however, this means they can only recover to the time of the last archive log.

Using Oracle INIT.ORA parameters, the destination and frequency of the archive logging can be controlled, although the size of the redo log plays more of a role in the frequency of archive logging than any initialization parameter.

The above text is an excerpt from Mike Ault’s Oracle DBA Made Simple by Rampant TechPress.

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