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RMAN 1.2 Backup Types

Physical and Logical Backups

  1. Copy of Datafile using an OS utility such as cp command.
  2. You can use this file to restore the database contents if you lose the disk file.
  3. Copy of the files like Datafiles, control files and redo log files.
  4. logical backups by using Oracle Data pump Export tool wherein you copy the definitions and contents all of the database’s logical componets such as table and so on.
  5. Its not complete backup and recovery solution.

Whole and Partial backups

  1. Backup of the entire database.
  2. Partial backup –> backup of a tablespace or datafile in a database.
  3. Datafile backup —> only a single OS file.
  4. Tablespace backup –> all the datafiles that are part of the tablespace.

Online and Offline Backups

  1. RMAN support both online ( HOT ) and offline ( COLD ) backups.
  2. An online backup is always inconsistent during a recovery , the application of the necessary archived log file will make the backup consistent.

Full and Incremental Backups

  1. It will contain complete backups of all the datafiles.
  2. It contain only the changed data blocks in the datafiles.
  3. You can make incremental backups only with the help of RMAN.

Consistent and Inconsistent Backups

What is SCN?

  1. SCN is an Oracle assigned number that indicates a committed version of a database.
  2. Its quite possible that different datafiles in the database might have a different SCN at any given point in time.
  3. If the SCN across all the datafiles are synchronized, it means that the data across the datafiles comes from a single point of time and thus, is consistent.
  4. During each checkpoint, the server makes all the datafiles SCN consistent w.r.t an identical SCN.
  5. It updates control file  with that SCN information.
  6. This synchronization of the SCN gives you a consistent backup of your database.

Inconsistent Backup

  1. If you backup your database while it’s running, you may end up with backups of the various data files at various time points and different SCN.
  2. This means your database are inconsistent, since the SCN aren’t identical across all the datafiles.
  3. If you’re using inconsistent backups, you must use the archive redo log files to make the data current and synchronize the SCN across the datafiles.
  4. If you’re using the RMAN offline backup, the database must be mounted before you can actually perform the RMAN backup. RMAN needs to update the target database control file.
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