Types of Backup Formats for Oracle

You can create and manage two types of backup copies with Oracle Recovery Manager: backup sets and image copies. Each type of copies has its own characteristics, advantages, and disadvantages.

Earlier, you learned that a backup set is a format used by RMAN to store backup information. You can use a backup set to back up either the data files or the archive logs associated with a database. A backup set can either be a full backup, meaning that all information in the target objects is backed up, or a type of incremental backup, meaning only data blocks that have changed are included in the backup set. An incremental backup backs up the blocks that have been changed since the last incremental backup, whereas a cumulative incremental backup includes all the blocks that have been changed since the last full backup. A backup set contains all the information needed to restore objects, including control information.

An image copy is different from a backup set, in that the image copy is essentially a copy of the database file.
You can make an image copy of a database using RMAN or standard file system commands. If you use operating system commands to create an image copy, the database will either have to be offline or you will have to use the alter database commands described in the previous lesson. You cannot perform incremental backups with an image copy. However, you can restore an image copy directly, without having to restore it.

The BACKUP command can create either backup sets or image copies. For disk, you can configure RMAN to create either backup sets or image copies as its default backup type with the CONFIGURE DEVICE TYPE DISK BACKUP TYPE TO command. The default backup type for disk is an uncompressed backup set.
Note: Because RMAN can write an image copy only to disk, the backup type for tape can only be a backup set.
RMAN can create backup sets using binary compression. You can configure RMAN to use compressed backup sets by default on a device type by specifying the COMPRESSED option in the BACKUP TYPE TO ... BACKUPSET clause. To disable compression, use the CONFIGURE DEVICE TYPE command with arguments specifying your other desired settings, but omit the COMPRESSED keyword.
To configure the default type of backup:

1. Start RMAN and connect to a target database and a recovery catalog (if used).
2. Configure backup sets or image copies as the default backup type.

The following examples configure the backup type for disk backups to copies and backup sets:

CONFIGURE DEVICE TYPE DISK BACKUP TYPE TO COPY; # image copies
CONFIGURE DEVICE TYPE DISK BACKUP TYPE TO BACKUPSET; # uncompressed

The following examples configure compression for backup sets:

CONFIGURE DEVICE TYPE DISK BACKUP TYPE TO COMPRESSED BACKUPSET;
CONFIGURE DEVICE TYPE sbt BACKUP TYPE TO COMPRESSED BACKUPSET;

Click the Quiz link below to review your knowledge of the different types of backups.
Oracle Backup Types - Quiz
In the next lesson, you will learn about the concept of channels and how channels can be used with backups.