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Use

The decision on whether to use the Oracle Recovery Manager (RMAN) and with which backup library, depends largely on the strategy that you use to back up your data. The best strategy depends on:

  • The size of the database

  • The amount of data added or changed each day

  • The backup media you use

  • Your security requirements

Features

The following table summarizes the main features of backup with RMAN:

Normal Backups

Full Backup (Level 0)

Incremental Backup (Level 1)

With

RMAN

You cannot use RMAN to make a normal backup to a remote disk, even with a backup library.

Without

RMAN

  • To local or remote tape devices, local or remote disks with BRBACKUP

  • Backup with external tool and BACKINT

  • To local or remote tape devices, local or remote disks with BRBACKUP followed by cataloging

  • Backup with external tool and BACKINT followed by cataloging

Not possible
Note

For more information on the backup types referred to above, see:

Incremental Backup Strategies with RMAN

You can perform incremental backups of the database with RMAN and BRBACKUP. RMAN offers the following types of incremental backup:

  • Several levels

  • Cumulative

  • Non-cumulative

The integration of RMAN into BRBACKUP is restricted to cumulative incremental backups at level 1. This means that, in the event of a recovery, only one incremental backup at the most has to be applied. In contrast to a full backup, an incremental backup only backs up the changes that have been made since the last full backup. This significantly reduces the amount of backup data. Therefore, we recommend this strategy particularly for large databases.

An incremental backup always requires an earlier full backup, that is, a level-0 backup. When RMAN backs up the database, it backs up all Oracle database blocks that have already been used. A subsequent incremental level-1 database backup backs up all Oracle database blocks that have changed since the last full backup. Changes to the whole database are taken into account.

Incremental backups at level 1 can only be made with RMAN. However, a full backup can also be made with BRBACKUP or with an external backup tool using BACKINT. In this case, BRBACKUP automatically catalogs the backup as a level-0 backup.

Note

You might not see a significant reduction in backup time by making an incremental backup. The reason is that it might take as much time to check whether a block has been used or changed as to simply back it up. This means that you only see a significant time reduction when the relatively low throughput of the tape devices is the reason for a long backup.

The problem can be solved by activating the Oracle block change tracking feature, as described in SAP Note 964619 Information published on SAP site.

Note

Using the incremental backup strategy, we recommend you to set a lock period for the tapes of at least 28 days, so that several generations of full backups are available. The offline redo log files must cover the period up to the oldest full backup - that is, both sets of tapes must have the same lock period - and must also be backed up daily.

After structural changes to the database, you can make incremental backups with RMAN and BRBACKUP. For more information, see RMAN Incremental Backups After Structural Changes.

Activities

This is a possible incremental backup scenario:

  • Sundays: full backup (level 0) of the database

  • Monday to Saturday: incremental backup (level 1) of the database

The tools used to implement this backup strategy depend on your specific requirements for backup media, volume of data, and so on.

For more information on incremental backups, see the Oracle documentation.