RMAN Incremental Backups Without a Backup Library (SAP Library - SAP Database Guide: Oracle (BC-DB-ORA-DBA))

RMAN Incremental Backups Without a Backup Library

Use

If you do not have a backup library, you can develop a strategy involving an incremental backup of your Oracle database by performing:

A full backup at level 0, which you can perform in one of the following ways:

To local disk with the Oracle Recovery Manager (RMAN), then copy it to tape using BRBACKUP

To local or remote disk or tape with BRBACKUP or an external tool (that is, without RMAN), then use RMAN to catalog the backup

An incremental backup at level 1 to local or remote disk, for which you always have to use RMAN, then copy to tape using BRBACKUP

For more information, see RMAN Backup Strategies.

Features

Full Backup at Level 0 to Local Disk with RMAN

You can make a full backup with RMAN and without a backup library only to local disk. You then use BRBACKUP to copy the disk backup to tape. This is a two-phase backup, that is, first a backup to disk, then a copy to tape.

It has the following advantages:

You can use RMAN functions, such as automatic block checks.

There is less redo information in an online full backup, since RMAN checks the consistency of the data at block level, so removing the need for the BEGIN/ END BACKUP commands.

It has the disadvantage that you need to copy the full backup to tape, which is extra work.

Full Backup at Level 0 with BRBACKUP or an External Tool, Without RMAN

You can make the full backup at level 0 without RMAN. After you have made the full backup – using BRBACKUP (with cpio or dd) or BACKINT and an external tool – BRBACKUP calls RMAN to catalog the backup as a level-0 backup.

This has the following advantages:

There is additional security when you restore or recover the backup. You can recover the database without RMAN because no save sets are formed during the full backup. In this case, the import of the redo log files created since the last backup replaces the restore of the last incremental backup.
Under certain conditions the backup can be quicker, since RMAN is not involved in the full backup at level 0. The data is backed up directly using cpio, dd, or BACKINT.

It has the following disadvantages:

You cannot use RMAN features such as the database block check.

The commands BEGIN BACKUP and END BACKUP are used in an online full backup, leading to extra redo log files. This data increases the load on the system and makes an "archiver stuck" error more likely. If you have an "archiver stuck" error, see SAP Note 316642.

If you make a recovery without RMAN you might have to apply a lot of redo log files since the full backup is usually only made once a week.

Incremental Backup at Level 1 to Disk with RMAN

You can make incremental backups at level 1 with RMAN and without a backup library, but only to local disk. There is no one-to-one copy of the database files. Instead, save sets are created, which means you can only recover the save sets of an incremental backup with RMAN. For more information, see RMAN Save-Set Grouping. In a second phase, you copy the incremental backup to tape with BRBACKUP. This is a two-phase backup, that is, first a disk backup, then a copy to tape.

Example

Here is an example of how you can perform the two stages in an incremental backup without backup library: a full backup at level 0 and an incremental backup at level 1.

Stage 1: Full Database Backup at Level 0 Without Backup Library

This graphic is explained in the accompanying text

As shown in the graphic, the full backup consists of the following phases:

Phase 1

BRBACKUP calls cpio, dd, or BACKINT to back up the database. cpio or dd read the data from the disk and write it to tape. If you use the BACKINT interface, the database file names are transferred to external backup software that then backs up the files to the backup medium.

Phase 2

BRBACKUP calls RMAN to automatically catalog the backup as a full backup (level 0). This means it can be used as a reference for later incremental backups.

Stage 2: Incremental Backup at Level 1 Without Backup Library

Since you cannot make an incremental backup directly to tape without RMAN, this stage is a two-phase backup (that is, a backup phase followed by a copy phase):

This graphic is explained in the accompanying text

As shown in the graphic, the full backup consists of the following phases:

Phase 1

BRBACKUP calls RMAN, which internally activates an Oracle server process to read the data from the Oracle database and save it to disk in a save set.

Phase 2

BRBACKUP calls cpio, dd, or BACKINT to copy the incremental save set from disk to the backup medium.

For more information, see RMAN Backup Strategies and Profile Parameters and BRBACKUP Command Options.