Set until time clause to restore controlfile

Question

Hello
How can I use "set until" clause to restore the controlfile ?
The database is already in archivelog mode.
RMAN>
run {
set until time "TO_DATE('2011-02-24 09:30:00','yyyy-mm-dd hh24:mi:ss')";
restore controlfile from autobackup;
RMAN>
RMAN> 2> 3> 4>
executing command: set until time
using target database control file instead of recovery catalog
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of set command at 02/24/2011 09:52:54
ORA-01507: database not mountedThis is the rman backup log:
Starting Control File and SPFILE Autobackup at 24-FEB-11
piece handle=/oracle/ora1020/dbs/c-1270860316-20110224-01 comment=NONE
Finished Control File and SPFILE Autobackup at 24-FEB-11I can also confirm that it was backed up.
ls -l /oracle/ora1020/dbs/c-1270860316-20110224-01
-rw-r-----  1 oracle dba 7143424 Feb 24 09:25 /oracle/ora1020/dbs/c-1270860316-20110224-01

Answer 1

For Datafiles and ArchiveLogs :
SET UNTIL works because RMAN can query the Controlfile (that is already present) {OR the Catalog, if available} to determine the Database Incaranation and identify all the BackupSets, BackupPieces and SCNs for datafiles.
For Controlfiles :
SET UNTIL needs to be able to query a source or determine a default location. If a Catalog is available, it can query the catalog. In the absence of the catalog, it can only determine the expected location to restore from on the basis of the AUTOBACKUP location and FORMAT.
When you have AutoBackup to Disk, using an FRA and have the AUTOBACKUP FORMAT set correctly you will notice that the controlfile backups go to a directory that has the date as part of the directory name. RMAN can "query" the backups it finds in each of the folders in the autobackup location and determine the correct piece to restore from. This is predicated on the FORMAT being the expected format. That is why the example also shows how you set the FORMAT before you do the restore -- to "tell" RMAN what format to expect. (Remember that it has no repository -- controlfile or catalog -- to query so it doesn't know the backup piece names, unless they follow the expected location and format !)
All of this works well on disk. On tape, it has to actually send it's requests to the Medial Management Layer -- it is the Media Management Layer that maintains the catalog of tapes and files on tapes. (Remember that RMAN still doesn't have a repository that it can query !).
Going back to my earlier comment that SET UNTIL is used for Datafiles and Archivelogs : Because it is much easier for RMAN to query a known repository for all the information it needs.
Hemant K Chitale