Recovering Databases with RMAN - OCP: Oracle Database 12c Administrator Certified Professional - page 222

The database DBID is included in the filename of the control-file auto-
backup backup set pieces (if you're not using the FRA). Thus, in a worst-
case situation, you can determine the DBID for your database by looking
at these files and determining the DBID from the filenames. If you are not
using the FRA, this is one very good reason to put control-file autobackups
in different directories for different databases!
Now that you have the DBID, you are ready to restore the database control file. To do
so, follow these steps:
1. Start up the database in NOMOUNT mode. This will start the database and load the
database parameter file. The FRA parameters will be set at this point.
2. Issue the SET DBID command to set the database DBID that RMAN will look for.
3. Set the control-file autobackup location with the SET CONTROLFILE AUTOBACKUP FOR-
MAT command.
4. Restore the control file with the RESTORE command.
5. Mount the database for recovery.
6. Issue the RECOVER DATABASE command.
7. Open the database using the ALTER DATABASE OPEN RESETLOGS command.
Here is an example of recovering a control file when the FRA is not in use:
RMAN> startup force nomount;
Oracle instance started
Total System Global Area 535662592 bytes
Fixed Size 1334380 bytes
Variable Size 369099668 bytes
Database Buffers 159383552 bytes
Redo Buffers 5844992 bytes
RMAN> Set dbid 437680418;
executing command: SET DBID
RMAN> set controlfile autobackup format for device type
disk to 'c:\oracle\controlfilebackup\%F';
executing command: SET CONTROLFILE AUTOBACKUP FORMAT
RMAN> Restore controlfile from autobackup;
Starting restore at 28-SEP-13
using channel ORA_DISK_1
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20130928
channel ORA_DISK_1: AUTOBACKUP found:
c:\oracle\controlfilebackup\c-437680418-20130928-04
channel ORA_DISK_1: restoring control file from AUTOBACKUP
c:\oracle\controlfilebackup\c-437680418-20130928-04