RMAN Recovery Scenario How to Restore a Database When Control Files are Lost in Oracle

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In this article, we will discuss how to recover a database control file from a trace in Oracle using the RMAN (Recovery Manager) tool. This is the second restore scenario in a series of videos on backup and restore scenarios.

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Understanding the Control File Loss Scenario

The control file is a crucial component of an Oracle database as it contains metadata about the database itself. If the control file is lost, the database cannot function properly. In this scenario, we will explore how to restore the control file using RMAN.

Step-by-Step Process

  1. Check the current location of the control files in your Oracle database. This can be done by running the following query:

SELECT name FROM v$controlfile;

  1. Delete the control files manually to simulate the control file loss. This can be done using the rm command. For example:

rm -i /path/to/controlfile1
rm -i /path/to/controlfile2

  1. Connect to the Oracle database and attempt to start the instance. However, you will encounter an error indicating that the control file cannot be found.

  2. Kill the ASM (Automatic Storage Management) instance to prevent any further operations on the database.

kill -9 <ASM_PID>

  1. Restart the database instance and attempt to mount the database. This operation will fail since the control file is missing.

  2. Open a separate admin prompt and connect to RMAN. Use the restore controlfile command to restore the control file from an auto backup. For example:

RMAN> restore controlfile from autobackup;

  1. RMAN will search for the auto backup in the recovery area and restore the control file.

  2. Verify the control file restoration by running the following query:

SELECT name FROM v$controlfile;

  1. Mount the database using the alter database mount command in either SQL or RMAN prompt.

  2. Once the database is mounted, restore the data files and recover the database using the appropriate RMAN commands.

  3. Finally, open the database with reset logs using the alter database open resetlogs command.

Conclusion

In this article, we explored the scenario of control file loss in an Oracle database and learned how to restore the control file using RMAN. By following the step-by-step process outlined above, you can recover a database when the control files are lost.

Please stay tuned for our next session, where we will cover the restoration of control files in an ASM Oracle Restart Service database or a RAC (Real Application Clusters) database.