RMAN(Recovery Manager)

  RMAN (Recovery Manager) is an Oracle Utility that can be backup, restore and recover the database file. The RMAN is a feature of the ORACLE database server and does not require separate installation.

RMAN introduced from oracle 8i in 1996

Every target database has to be registered with a catalog database

We can invoke RMAN as a command-line executable from the operating system.

In case of Cold or hot backup 

It is like blind backup or mirror image

ie) Size of backup equal to database size

In RMAN it is Content copy backup, that is Only used blocks backup

For Example:

In 100GB database 

only 60% are used blocks, That is used blocks = 60GB in  that 60GB Used blocks, changed or modified blocks are of only 1GB

The RMAN  complte backup includes 60 GB & incremental backup includes 1 GB

In 10g compressed backup is possible and can do point in time done by tablespace by using RMAN

Concepts:

• RMAN Keeps a recovery of all the databases that are registered with the catalog
• When RMAN is invoked to backup or recover a database, it verifies the target database with the stored database id available in the RMAN catalog.
• If it matches then RMAN establishes two server sessions with the target database.
• A channel is a remote procedure call (RPC) to the target. database using PL/SQL interface to perform backup and recovery operation.
• RMAN compiles the command and executes it on the target database with the summary of actions, If booked up to these files are called 'backup pieces' 
• to backup to tape drive/tape library, We need the "Media Manager" like VNB or LSM
• Execution of every RMAN backup command produces a backup set that is a logical grouping of one or more physical files  are called "backup Pieces"
• RMAN backup is going to be the content backup,  not mirror image but only used blocks, thus, it is going to be a lot smaller and faster compared to cold/ hot backup.

Advantages:

• Corrupt blocks identification
•  Automated scheduled backups
• Incremental backup --- only those blocks which are changed since the last backup
• Automated scheduled backups
• trass check --- Once the backup is over, again checking against the original file
• Can generate logs on backup and recovery
• can share pr-configured scripts in the catalog database that can run anytime
• A tag can be specified to the backup file
• file set which can be used even at the time of restore instead of filename
• Tablespace point in time recovery is possible, In case of cold and hot backups only database point in time recovery is possible
• Create a duplicate database of the production database for developers / QA People
• Multiple destinations can be mentioned
• Cleanup Procedures can be implemented, After performing RMAN successfully backup let RMAN get rid of any obsolete archived log files (expired).

Pre-requirements:

• Every target database must be registered against the catalog database.
• In the catalog database, a separate tablespace must be created to hold catalog schemas owner
• A user should be created in the Catalog database with connect, resource, recovery _catalog_owner privileges