Can one restore RMAN backups without a CONTROLFILE and RECOVERY CATALOG?

Details of RMAN backups are stored in the database control files and optionally a Recovery Catalog. If both these are gone, RMAN cannot restore the database.

In such a situation one must extract a control file (or other files) from the backup pieces written out when the last backup was taken.

Let's look at an example:

Let's take a backup (partial in our case for ilustrative purposes):

$ rman target / nocatalog
Recovery Manager: Release 10.1.0.2.0 - 64bit Production
Copyright (c) 1995, 2004, Oracle. All rights reserved.
connected to target database: ORCL (DBID=1046662649)
using target database controlfile instead of recovery catalog

RMAN> backup datafile 1;
Starting backup at 20-AUG-04
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=146 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=/oradata/orcl/system01.dbf
channel ORA_DISK_1: starting piece 1 at 20-AUG-04
channel ORA_DISK_1: finished piece 1 at 20-AUG-04
piece handle= /flash_recovery_area/ORCL/backupset/2004_08_20/o1_mf_nnndf_TAG20040820T153256_0lczd9tf_.bkp
comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:45
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current controlfile in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 20-AUG-04
channel ORA_DISK_1: finished piece 1 at 20-AUG-04
piece handle=/flash_recovery_area/ORCL/backupset/2004_08_20/o1_mf_ncsnf_TAG20040820T153256_0lczfrx8_.bkp
comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:04
Finished backup at 20-AUG-04

Now, let's destroy one of the control files:
SQL> show parameters CONTROL_FILES
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
control_files string /oradata/orcl/control01.ctl,
/oradata/orcl/control02.ctl,
/oradata/orcl/control03.ctl
SQL> shutdown abort;
ORACLE instance shut down.
SQL> ! mv /oradata/orcl/control01.ctl /tmp/control01.ctl

Now, let's see if we can restore it. First we need to start the databaase in NOMOUNT mode:

SQL> startup NOMOUNT
ORACLE instance started.
Total System Global Area 289406976 bytes
Fixed Size 1301536 bytes
Variable Size 262677472 bytes
Database Buffers 25165824 bytes
Redo Buffers 262144 bytes

Now, from SQL*Plus, run the following PL/SQL block to restore the file:

DECLARE
v_devtype VARCHAR2(100);
v_done BOOLEAN;
v_maxPieces NUMBER;
TYPE t_pieceName IS TABLE OF varchar2(255) INDEX BY binary_integer;
v_pieceName t_pieceName;
BEGIN
-- Define the backup pieces... (names from the RMAN Log file)
v_pieceName(1) :=
'/flash_recovery_area/ORCL/backupset/2004_08_20/o1_mf_ncsnf_TAG20040820T153256_0lczfrx8_.bkp';
v_pieceName(2) :=
'/flash_recovery_area/ORCL/backupset/2004_08_20/o1_mf_nnndf_TAG20040820T153256_0lczd9tf_.bkp';
v_maxPieces := 2;
-- Allocate a channel... (Use type=>null for DISK, type=>'sbt_tape' for TAPE)
v_devtype := DBMS_BACKUP_RESTORE.deviceAllocate(type=>NULL, ident=>'d1');
-- Restore the first Control File...
DBMS_BACKUP_RESTORE.restoreSetDataFile;
-- CFNAME mist be the exact path and filename of a controlfile taht was backed-up
DBMS_BACKUP_RESTORE.restoreControlFileTo(cfname=>'/app/oracle/oradata/orcl/control01.ctl');
dbms_output.put_line('Start restoring 'v_maxPieces' pieces.');
FOR i IN 1..v_maxPieces LOOP
dbms_output.put_line('Restoring from piece 'v_pieceName(i));
DBMS_BACKUP_RESTORE.restoreBackupPiece(handle=>v_pieceName(i), done=>v_done,
params=>null);
exit when v_done;
END LOOP;
-- Deallocate the channel...
DBMS_BACKUP_RESTORE.deviceDeAllocate('d1');
EXCEPTION
WHEN OTHERS THEN
DBMS_BACKUP_RESTORE.deviceDeAllocate;
RAISE;
END;
/

Let's see if the controlfile was restored:

SQL> ! ls -l /oradata/orcl/control01.ctl
-rw-r----- 1 oracle dba 3096576 Aug 20 16:45 /oradata/orcl/control01.ctl

We should now be able to MOUNT the database and continue recovery...

SQL> ! cp /oradata/orcl/control01.ctl /oradata/orcl/control02.ctl
SQL> ! cp /oradata/orcl/control01.ctl /oradata/orcl/control03.ctl
SQL> alter database mount;
SQL> recover database using backup controlfile;
ORA-00279: change 7917452 generated at 08/20/2004 16:40:59 needed for thread 1
ORA-00289: suggestion :
/flash_recovery_area/ORCL/archivelog/2004_08_20/o1_mf_1_671_%u_.arc
ORA-00280: change 7917452 for thread 1 is in sequence #671
Specify log: {=suggested filename AUTO CANCEL}
/oradata/orcl/redo02.log
Log applied.
Media recovery complete.
Database altered.
SQL> alter database open resetlogs;
Database altered.