How to recover the Control file in RMAN Oracle

Find the location of your Control Files and drop them. 

 SQL> select name from v$controlfile;

NAME
--------------------------------------------------------------------------------
/opt/oracle/oradata/oracle/control01.ctl
/opt/oracle/oradata/oracle/control02.ctl

bash:> rm -rf /opt/oracle/oradata/oracle/control01.ctl /opt/oracle/oradata/oracle/control02.ctl
Next simulate the error using a command that will need to alter the control file. 
 SQL> alter tablespace system online;
alter tablespace system online
*
ERROR at line 1:
ORA-00210: cannot open the specified control file
ORA-00202: control file: '/opt/oracle/oradata/oracle/control01.ctl'
ORA-27041: unable to open file
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Shutdown the database and start it in nomount mode. 
 SQL> shutdown abort;
ORACLE instance shut down.


SQL> startup nomount;
ORACLE instance started.
Total System Global Area  417546240 bytes
Fixed Size                  2213936 bytes
Variable Size             314574800 bytes
Database Buffers           96468992 bytes
Redo Buffers                4288512 bytes
Database must be in nomount mode as it will not reach the stage where the controlfile is needed. Now let's go to our RMAN tool and restore our control file. A very important step here is that you need to provide your database DBID. If you don't have in your database config documentation or any old RMAN logs or you don't use Recovery catalog then you can try to use the "strings" tool using the syntax : "strings undotbs01.dbf | grep MAXVALUE" this will return the value of your DBID. 
RMAN> set DBID=1423547369
executing command: SET DBID

RMAN> restore controlfile from autobackup;
Starting restore at 25-OCT-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=19 device type=DISK
recovery area destination: /opt/oracle/flash_recovery_area
database name (or database unique name) used for search: DB1
channel ORA_DISK_1: AUTOBACKUP /opt/oracle/flash_recovery_area/DB1/autobackup/2013_10_24/o1_mf_s_829684173_96m5hgd9_.bkp found in the recovery area
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20131025
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20131024
channel ORA_DISK_1: restoring control file from AUTOBACKUP /opt/oracle/flash_recovery_area/DB1/autobackup/2013_10_24/o1_mf_s_829684173_96m5hgd9_.bkp
channel ORA_DISK_1: control file restore from AUTOBACKUP complete
output file name=/opt/oracle/oradata/db1/control01.ctl
output file name=/opt/oracle/flash_recovery_area/db1/control02.ctl
Finished restore at 25-OCT-13
This is only possible if you have your RMAN settings controlfile autobackup on. Next mount the database(which means that controlfile will be validated) 
 RMAN> alter database mount;

database mounted
released channel: ORA_DISK_1
Next we need to recover and open the database. 
 RMAN> recover database;

Starting recover at 25-OCT-13
Starting implicit crosscheck backup at 25-OCT-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=19 device type=DISK
Crosschecked 3 objects
Finished implicit crosscheck backup at 25-OCT-13
Starting implicit crosscheck copy at 25-OCT-13
using channel ORA_DISK_1
Finished implicit crosscheck copy at 25-OCT-13
searching for all files in the recovery area
cataloging files...
cataloging done
List of Cataloged Files
=======================
File Name: /opt/oracle/flash_recovery_area/DB1/autobackup/2013_10_24/o1_mf_s_829684173_96m5hgd9_.bkp
using channel ORA_DISK_1
starting media recovery
archived log for thread 1 with sequence 3 is already on disk as file /opt/oracle/flash_recovery_area/DB1/archivelog/2013_10_24/o1_mf_1_3_96m5hc6s_.arc
archived log for thread 1 with sequence 4 is already on disk as file /opt/oracle/oradata/db1/redo01.log
archived log file name=/opt/oracle/flash_recovery_area/DB1/archivelog/2013_10_24/o1_mf_1_3_96m5hc6s_.arc thread=1 sequence=3
archived log file name=/opt/oracle/oradata/db1/redo01.log thread=1 sequence=4
media recovery complete, elapsed time: 00:00:01
Finished recover at 25-OCT-13



RMAN> alter database open resetlogs;

database opened
Is good to remember that we can run sql commands in RMAN.

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