Problem:Restore of the Control File from Control File Autobackup

Impact:control file is lost or damage and and database cannot be started.

Solution:
If we dont have recovery catalog and want to restore the control file from autobackup, the database must be in a NOMOUNT state. You must first set the DBID for your database, and then use the RESTORE CONTROLFILE FROM AUTOBACKUP command:

RMAN> SET DBID 320066378;
RMAN> RUN {
    SET CONTROLFILE AUTOBACKUP FORMAT 
          FOR DEVICE TYPE DISK TO 'autobackup_format';
    RESTORE CONTROLFILE FROM AUTOBACKUP;
    }