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RMAN

Why RMAN

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Why we should use RMAN ?

 

Since version 8.0 Oracle has introduced Recovery Manager, an utility to backup and recover the database. Despite a painful and buggy start there are these days not that many reasons left why you should not backup and recover with RMAN. Some of the advantages of RMAN :

1. RMAN does not  put a tablespace in backup mode while backing up the data files from this tablespace  ( alter tablespace tablespace_name begin backup nor alter tablespace tablespace_name end backup is necessary ) as such there is no extra redo generation during hot backup nor there are issues with tablespaces which remain in backup mode.
 
2. RMAN makes it possible to implement an incremental backup strategy and to take full benefit from block change tracking. Block change tracking is a new feature of 10G R1. Previously RMAN had to read the entire data file even for incremental backups. With BCT the block change tracking file is read and only the changed data blocks are read by the backup process.

3. RMAN makes it possible to detect and repair online block corruption. ( physical and logical ). RMAN reads the database blocks in the same way as SQL does.

4. RMAN will only back up the already used blocks no matter what the data file size is about.

5. RMAN makes it possible to use compressed backup sets. RMAN compression is a 10G R1 new feature.

6. RMAN makes it possible to use encryption . RMAN encryption is a 10G R2 new feature. 

7. RMAN makes it easy to duplicate a database on another host.

8. RMAN makes it easy to duplicate a database on the same host.

9. RMAN makes it easy to clone an active database ( 11G R1 feature )

10. RMAN makes it easy to create a standby database.

11. RMAN switches automatic redologs prior to backing up archived redo logs.

12. RMAN manages the delete archivelog policy. The archive log deletion policy configure archive log deletion to applied on standby allows automatic purging of archived redo logs assuming they have been recovered at the level of the standby database. As such one can avoid a still required archived redo log is purged by accident.

13. RMAN does not backup read only tablespaces assuming the skip readonly option is used.

14. RMAN has commands to check physical and logical integrity of database files, backup sets and control files.

15. RMAN allows backup parallellism with multiple channels and section sizes.

16. RMAN allows cross platform data file (endian) format conversion. Example : database files from a 64 BIT Unix system can be converted to Windows 32 BIT format. ( 10G R1 feature )