Oracle RMAN Backup Types

In this article, we are going to discuss oracle rman backup types. As you know RMAN is a utility of oracle database which is used to take Database backup.

The RMAN backup is two types:

• Full Backup
• Incremental Backup

Full RMAN backup

A complete backup differs from a full database backup. A full backup of the data file is a backup that includes every data block that is used in the file. RMAN copies all blocks to the backup set, or the image copy, leaving out only the data block that has never been utilized. In a full image copy that is, all contents of the image are replicated exactly. Full backups cannot be used as part of an incremental backup plan or be the source for a subsequent incremental backup.

Incremental Backup

An incremental backup can be a level 0 backup which contains every block of the data files, excluding blocks that have not been used, or a Level 1 backup, which contains only the blocks that have been modified in the past since the backup was made. A level zero incremental backup is similar to a full backup. It is the only distinction being that the backup at level 0 may serve as the base for level 1 backups, however, a complete backup cannot ever be used as the base for the level 1 backup.

Incremental backups can be specified with the INCREMENTAL keyword in the BACKUP command. It is possible to specify INCREMENTAL LEVEL as 0 or 1.

RMAN utility multiple incremental database backups are listed below:

Differential: It is the most common kind of incremental backup which protects all the blocks that have changed in the last incremental backup, at either level 1 or 0.

Cumulative: Back up all changed blocks after the most recent backup at level 0.

Examples of incremental backup commands

Using below examples you can perform the RMAN Backup Types:

Incremental Level 0

RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE;

Differential incremental backup Level 1

RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;

Cumulative incremental backup Level 1

RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;

RMAN creates full backups by default when neither FULL nor INCREMENTAL are specified. Block compression that is not used causes the never-written blocks to not be skipped while backing up data backup sets to files even for backups with complete backups.

A complete backup does not have any impact over subsequent backups and therefore is not as part of an incremental backup plan However, a complete image copy backup is periodically updated by applying incremental backups using a RECOVER command.

Fast Incremental Database Backup

The purpose of an incremental backup is to save only the data blocks that have changed since the previous backup. You can utilize RMAN in order to make incremental backups for tablespaces, tables, data files, or even the entire database. When you create the incremental backup RMAN examines every block in data files to determine which ones have changed since the previous backup. The backup is, therefore, smaller because only those blocks that have changed are saved. This also speeds up recovery since there are fewer blocks that need to be restored.

You can make a quick incremental backup by enabling a tracker of block changes. Block change tracking records to a file the physical location of every block that has altered. When it's time to do an incremental backup RMAN will look through the file that tracks block changes and back up only the blocks that are referenced there It does not need to go through every block to determine whether it has changed since the previous backup. This helps to make the incremental backup more efficient.

How to Enabling Fast Incremental Backup

You can enable blocking change tracking on your Database Control home page. Navigate to Availability > Backup Settings > Policy. There is no need to define the file's block change tracking location if the initialization parameter is enabled because the file was created in the form of the Oracle Managed File (OMF) file within the DB_CREATE_FILE_DEST directory. You are able to, however, choose your block's name. tracking file and place it in the location you like.

You can also activate or deactivate this feature using the ALTER DATABASE command. If the file for tracking changes is kept in the database area along with the database files, it is deleted after you deactivate change tracking.

Example:

ALTER DATABASE
{ENABLE|DISABLE} BLOCK CHANGE TRACKING
[USING FILE '/u01/rman_bct.ctl']

Command:

SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE '/u01/rman_bct.ctl';

In future if you want to rename the block change tracking file then use ALTER DATABASE RENAME commands. During this activity the database must be in mount mode to rename tracking file. You can use below command to rename the tracking file.

SQL> ALTER DATABASE RENAME 'CURRENT_FILE_NAME_WITH_LOCATION' TO 'NEW_FILE_NAME_LOCATION';

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