Recovery :- Open Database Recovery with Offline Tablespace

 'Data recovery' refers to the process of recovering data from a hard drive, removable disk, or other type of electronic storage media when the data is no longer accessible via normal means.Data recovery can be a simple process in many cases, and in some cases may require exhaustive, detailed work to recover the data.Here we are trying to explain Open Database Recovery with Offline Tablespaces

If your system suffers a media failure but the database stays up, you can perform an open database recovery and recover only the tablespaces that are damaged. Users can continue to access the online tablespaces and datafiles that were not damaged by the failure. Oracle automatically takes damaged datafiles offline.

Follow these steps to execute an open database recovery with offline tablespaces: 

1) The database should be started and open. 
2) Take all tablespaces containing damaged datafiles offline using the ALTER TABLESPACE tablespace_name OFFLINE command. You can query the V$DATAFILE view to see which datafiles are offline.
3) Correct the problem that caused the media failure. If the problem cannot be corrected in a reasonable amount of time, your other option is to restore the damaged files to another location. Follow these three steps to relocate the datafile(s):
  • Make sure the tablespace that contains the datafiles is offline.
  • Make sure that the new, fully specified file names are different from the old file names.
  • Use the ALTER DATABASE command with the RENAME FILE option to change the file names within the database.
If the media problem can be corrected, restore the most recent backup files of only the datafiles damaged by the media failure. Remember that the database is open. Do NOT try to restore undamaged datafiles, logfiles, or control files!

4) Use the RECOVER TABLESPACE command to start offline tablespace recovery of all damaged datafiles in one or more offline tablespaces.
Oracle will now start the roll forward by applying the archived redo logfiles and the online redo logfile. If AUTORECOVERY is set to ON, the applying of the log files is automatic. If it is not set to ON, you will be prompted for each logfile.

5) The damaged tablespaces of the open database are now recovered up to the point of failure. You can bring the offline tablespaces online using ALTER TABLESPACE command with the ONLINE option.

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