Understanding Recovery Manager
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by Debjani Mallick
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Backup Types in RMAN

With RMAN one can perform various types of backup as shown below.

·         Open or closed – Open backup is the backup taken when the database is open: a backup of online, read/write data files. Closed backup is the backup of any part of the target database when it is mounted but not open.

·         Full or incremental – A backup of type full is the back up of a data file that contains every allocated block in the file being backed up. And an incremental backup is either a level 0 backup or a level 1 backup.

·         Consistent or inconsistent – A consistent backup is the backup taken when the database is mounted but is not open after a normal shutdown. Whereas an inconsistent backup is the backup taken of any part of target database when the database is open or when a crash occurred, etc.

Backup database using RMAN

In non-archive mode, using dos prompt type:

RMAN

the RMAN prompt gets displayed.

Listing 1

RMAN>Connect Target 
Connect to target database:Xxx<Dbid:123456789>

This is using the database of target file rather than the recovery catalog.

A Dbid stands for Database Identifier which is a unique identifier and found in all datafile headers and control files. It is used to identify a file belongs to which database.

A simple example of taking backup in non-archived mode:

Listing 2

shutdown immediate; //shuts down the database
startup mount;
backup database; //starts backing up the database
alter database open;

In archivelog mode, the same command can also be fired to backup the whole database.

Listing 3

backup database plus archivelog;

The backup command can backup the following type of files:

·         Database (which includes all datafiles as well as the current control file and current server parameter file)

·         Tablespaces, except for locally-managed temporary tablespaces

·         Current server parameter file

·         Current control file

·         Backup sets

·         Current datafiles

·         Archived redo logs

RMAN does not back up the following:

·         Online redo logs

·         Transported tablespaces before they have been made read/write

·         Client-side initialization parameter files, etc

Restore database using RMAN

Restoring and recovering a database using RMAN uses even more simple commands than backup.

Listing 4

restore database;
recover database;

RMAN has the intelligence to find out which datafiles are to be recovered or restored and the location of backed up files.


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