To recover the database with an autobackup of the control file without a recovery catalog:

Start RMAN and connect to the target database. For example, run: CONNECT TARGET /

Start the target instance without mounting the database. For example: STARTUP NOMOUNT;

Set the database identifier for the target database with SET DBID. RMAN displays the DBID whenever you connect to the target. You can also obtain it by running LIST, querying the catalog, or looking at the filenames of control file autobackup. (refer to "Restoring When Multiple Databases in the Catalog Share the Same Name: Example"). For example, run: SET DBID 676549873;

Restore the autobackup control file, then perform recovery. Do the following:
Optionally, specify the most recent backup time stamp that RMAN can use when searching for a control file autobackup to restore.
If a nondefault format was used to create the control file, then specify a nondefault format for the restore of the control file.
If the channel that created the control file autobackup was device type sbt, then you must allocate one or more sbt channels. Because no repository is available, you cannot use automatic channels. If the autobackup was created on a disk channel, however, then you do not need to manually allocate a channel.
Restore the autobackup of the control file, optionally setting the maximum number of days backward that RMAN can search (up to 366) and the initial sequence number that it should use in its search for the first day.
Mount the database. Note that because the repository is now available, any automatic channels that you configured are also available.
If the online logs are inaccessible, then restore and recover the database as described in "Performing Incomplete Restore and Recovery". You must terminate recovery by setting the UNTIL clause to a time, log sequence, or SCN before the online redo logs. If the online logs are usable, then restore and recover the database as described in "Performing Complete Restore and Recovery".
In this example, the online redo logs have been lost. This example limits the restore of the control file autobackup, then performs recovery of the database to log sequence 13243, which is the most recent archived log:RUN
{
# Optionally, set upper limit for eligible time stamps of control file backups
# SET UNTIL TIME '09/10/2000 13:45:00';
# Specify a nondefault autobackup format only if required
# SET CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '?/oradata/%F.bck';
ALLOCATE CHANNEL c1 DEVICE TYPE sbt; # manually allocate one or more channels
RESTORE CONTROLFILE FROM AUTOBACKUP
MAXSEQ 100 # start at sequence 100 and count down
MAXDAYS 180; # start at UNTIL TIME and search back 6 months
ALTER DATABASE MOUNT DATABASE;
}
# uses automatic channels configured in restored control file
RESTORE DATABASE UNTIL SEQUENCE 13243;
RECOVER DATABASE UNTIL SEQUENCE 13243; # recovers to most recent archived log

If recovery was successful, then open the database and reset the online logs: ALTER DATABASE OPEN RESETLOGS;

It is recommended that you immediately back up the database, preferably with the database mounted (to avoid possible data loss in an open database). Because the database is a new incarnation, the backups made before the RESETLOGS are not easily usable. For example, enter: SHUTDOWN IMMEDIATE
STARTUP MOUNT
BACKUP DATABASE;
ALTER DATABASE OPEN;