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BACKUP CONTROLFILE RECOVERY

Expert Oracle Tips by Burleson Consulting

April 7, 2011

 

When performing an RMAN recovery with only a single controlfile, you may want to issue the USING BACKUP CONTROLFILE RMAN RECOVER DATABASE command option.  

If you must use a control file restored from the backup, you will want to use the USING BACKUP CONTROLFILE option of the recover command.

If you are using a backup control file with an incomplete recovery, then specify the USING BACKUP CONTROLFILE option in the RECOVER command.

SQL> RECOVER DATABASE UNTIL CANCEL USING BACKUP CONTROLFILE;
SQL> RECOVER DATABASE USING BACKUP CONTROLFILE UNTIL CANCEL;

The Oracle documentation notes restrictions on doing a BACKUP CONTROLFILE RECOVERY.   The following notes and restrictions apply regardless of whether you use a recovery catalog:  

  • You must run the RECOVER command after restoring a backup control file, even if no datafiles have been restored.  
  • You must open the database with the RESETLOGS option after performing either complete or point-in-time recovery with a backup control file.  
  • If the online redo logs are inaccessible, then you must perform incomplete recovery to an SCN before the earliest SCN in the online redo logs. This limitation is necessary because RMAN does not back up online logs.  
  • During recovery, RMAN automatically searches for online and archived redo logs that are not recorded in the RMAN repository, and catalogs any that it finds so that it can use them in recovery.  

RMAN attempts to find a valid archived log in any of the current archiving destinations with the current log format. The current format is specified in the initialization parameter file used to start the instance (or all instances in a Real Application Clusters installation). Similarly, RMAN attempts to find the online redo logs by using the filenames as specified in the control file.  

If you changed the archiving destination or format during recovery, or if you added new online log members after the backup of the control file, then RMAN may not be able to automatically catalog a needed online or archived log. In this situation, RMAN reports errors similar to the following:  

RMAN-00571:===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of recover command at 08/29/2001 14:23:09
RMAN-06054: media recovery requesting unknown log: thread 1 scn 86945


The following excerpt is from the exciting book from Kamran Agayev A. and Aman Sharma: Oracle Backup & Recovery: Expert Secrets for Using RMAN and Data Pump.  See the book for the scripts and output results associated with the steps listed below:

Scenario 1:  Bob took a binary backup of the controlfile. The next day he loses all controlfiles of the database due to the media failure. As he has only the binary copy of the controlfile, he restores it and recovers the database.

  1. Take a binary backup of the controlfile and delete all controlfiles. Then shut down and start up the database ...

    This results in the following error:

    ORA-00205: error in identifying control file, check alert log for more info

  2. Copy the binary backup of controlfile to the original controlfile?s destination and mount the database ...
  3. If you try to open the database, you get the message that you must use the resetlogs option. If you use the resetlogs option, you are asked to perform a recovery. If you try to recover the database, you are asked to use the USING BACKUP CONTROLFILE clause. So you need to use the recover database using backup controlfile command to tell Oracle that you are trying to recover the database from the binary copy of the controlfile ...

By using this command, Oracle asks you to provide the changes made after the backup of the controlfile was taken. In this scenario, you are prompted to provide the redo log file name that contains the changes of the scn value 470859. To get the correct file which contains the changes made after the specified scn, you need to query both archived redo logs and online redo log files. In this scenario, as you have not any archived redo log files generated, query the v$log view: ...

To see more, order your copy of the book now!


 

 

Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  and include the URL for the page.


                    









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