Mechanism followed by RMAN Restore & Recovery.

Mechanism followed by RMAN Restore & Recovery.

•If we simply use RESTORE command then RMAN directs a server session to restore the file to default location that is overwrite the existing file.

•If we use RESTORE command with SET NEWNAME option then RMAN restore the file with specified location.

Example: RUN {
SET NEWNAME FOR DATAFILE '/oradata/datafile/1.dbf' TO '/tmp/1.dbf';
RESTORE DATAFILE '/oradata/datafile/1.dbf';
}

In this case, RMAN restore /oradata/datafile/1.dbf to /tmp/1.dbf
•RMAN always restore data file as image copy.

•After restoring a datafile to a new location if you want to use that then use the SWITCH command in order to update control file. RMAN SWITCH command is equivalent to SQL statement ALTER DATABASE RENAME FILE command.

Example: SWITCH DATAFILE '/oradata/datafile/1.dbf' TO DATAFILECOPY '/tmp/1.dbf';

•RMAN always select the most recent backup while restoring. If two backups are in the same point then RMAN prefers to use image copies over backup sets because RMAN can restore more quickly from image copies than from backup sets.

•During RESTORE operation if RMAN fails the restore one copy then i automatically searches other usable copy. If there is no backup exist then RMAN try to re-create the datafile.

•RMAN uses restore optimization to avoid restoring datafiles from backup when possible. If a datafile is already present in the correct location and its header contains the expected information, then RMAN does not restore the datafile from backup. However you can override this behavior by FORCE option of RESTORE command.

•If RMAN has a choice between archived redo logs and incremental backups then RMAN always choice incremental backups during recovery.If overlapping levels of incremental backups are available then RMAN choose the longest covering one.