Another issue is that RMAN is simpler to operate if its catalog is current and available—RMAN knows where the backup files and archive logs are located. If you are taking backups to disk and then outside of RMAN separately writing these backups to tape, you often end up having to manually perform the necessary restores before RMAN can use them.

Oracle Corporation continues to enhance RMAN in every release and Oracle 10g is no exception. In the limited space here, I would like to briefly highlight three applicable enhancements:

• RMAN in Oracle 10g is now able to backup and restore using compressed disk files using the “as compressed backupset” syntax. For example:

  RMAN> backup as compressed backupset database;

• Prior to Oracle 10g, RMAN incremental backups resulted in smaller backup files but were often not much faster than full backups because RMAN needed to read every block in the database to decide if it needed to be backed up. Oracle 10g provides a way for the database to track which blocks have been modified so RMAN can now take truly incremental backups—just reading and writing the modified blocks. If a database only changes by relatively small amounts on a daily basis this can be a dramatic resource saver. The status of block tracking can be confirmed by querying the v$block_change_tracking view. Tracking takes place in a separately allocated journal file and is specified with a statement such as:

  SQL> alter database enable block change tracking using file 'file_path';

  According to Metalink note 271197.1, incremental backups are available with Oracle 10g Standard Edition. Previous versions of Oracle required Enterprise Edition for this feature.

• RMAN in Oracle 10g is able to merge an incremental backup into an existing level-0 image copy already on disk. This means we no longer need to hold both the original level-0 backup and the incremental backup on disk, and that subsequent recovery will be faster because the incremental is already applied. This allows you to take regular incremental backups but have the advantage of a recent full level-0 image copy available. Unfortunately, the merging can only take place when using image copies rather than backupsets and image copies cannot (currently) be compressed. Thus at the moment you can either compress your disk backups or merge in an incremental backup—but not both. The merging is performed with a command such as:

  RMAN> recover copy of database with tag 'latest_full';

In summary, whether or not you should switch to RMAN depends on which release of Oracle you are using and which features are important to you. In an Oracle 9i environment you might want to stick with conventional hot backups if they are currently implemented and you don’t require any of RMAN’s existing capabilities. However, in an Oracle 10g environment, I would seriously consider switching to RMAN. Disk backups with RMAN are more practical in Oracle 10g and the incremental backup feature may save significant resources.