RMAN -Introduction

RMAN

RMAN : Recovery Manager

RMAN Components

RMAN is an Oracle Utility that can backup, restore and recover database files. The RMAN executable is named rman and can be found in $ORACLE_HOME/bin directory and is installed by default with Oracle 10g, 9i and 8i Standard and Enterprise editions.

Every Target Database has to be registered in the catalog database. We can invoke command line executables from the operating system.

In case of cold and hot backup it is like blind backup or mirror image

i.e size of backup is equal to database size.

But in case of RMAN, t is content copy backup i.e only used blocks backup.

Example:

In 100 GB database only 60% are used blocks i.e used blocks =60 GB

In that 60 GB of used blocks, changed or modified blocks are of only 1 GB

Complete backup includes 60GB

Incremental backup includes 1GB.

Concepts:

  1. RMAN keeps a record of all target databases that are registered with catalog database.
  2. When RMAN is invoked to backup or recover a database, it verifies the largest database with stored database if available in the RMAN Catalog.
  3. If its matches RMAN establishes two server session with target database.
  4. A channel is a remote procedural call to the target database using pl/sql interace to perform backup and recovery operations.
  5. RMAN Compiles the command and executed it on the target database with the summary of actions. Backedup to these files are called backup pieces. To backup to tape drive/tape library we need the media manager.
  6. Execution of every RMAN backup command produces a backup set that is a logical grouping of one more physical files called backup pieces.
  7. RMAN Backup s going to be content backup not mirror image but only used blocks are backed up. Thus RMAN is smaller and much faster when compared to other backups.

Advantages:

  1. Centralized backup and recovery and this recovery is across enterprise database.
  2. Incremental backups ñonly those blocks which are changed since last backup
  3. Corrupt block identification
  4. Automated scheduled backups
  5. Cross check ñ Once backup is over again checking the consistency of original files.
  6. Can generate logs on backup and recovery.
  7. Can report the summary information.
  8. Can store preconfigured scripts which can be run at any time.
  9. A log can specify to the backup file / files set which can be used even at the time of restore instead of filename.
  10. Tablespace point in time recovery is possible .
  11. Create duplicate database of production database for developers /QA people/
  12. Multiple destinations can be mentioned.
  13. Cleanup procedures can be implemented after performing RMAN successful backup. letís get rid of obsolete archive log files.

Pre -requirements:

  1. Every Target must be registered in the catalog database
  2. In the catalog database a separate tablespace must be created to hold catalog schema owner.
  3. A user should be created in the catalog database with connect, resource, recovery_catalog_owner privileges.