Control File Backups

Question

Hello-
I was looking over some configurations that was setup by another DBA.
There are 3 control files created but they all are on the same disk/directory.
Control file auto backup is on to tape.
If there was a hardware failure and all three control were corrupted/lost then a backup would be used but
full recovery and RESETLOGS would be needed which would lead to redo data loss.
If I configured 1 control file on a seperate disk. I would be able to copy this one and create 3 files again and the database
would be started again without needing recovery if all else was fine.
If the control keeps track of redo logs SCN, Archive logs history and RMAN backups when these change then wouldn't another control file backup/ trace need to be done ?
Control File Trace only alllows to rebuild the database not to copy. How often is the need to taken ? Every change in the database ?
Backup to the Flash Recovery is another backup not an updated copy to copy from but to restore/recovery with.
Do have have these theories correct and my best setup would to send at least one to another disk.
Thanks-

Answer 1

If there was a hardware failure and all three control were corrupted/lost then a backup would be used but
full recovery and RESETLOGS would be needed which would lead to redo data loss. No. If you lose all three controlfiles, you either
a. RESTORE a backup of the controlfile
OR
b. CREATE CONTROLFILE (from a script)
In either case, you do NOT need to do an INCOMPLETE Recovery. You will be doing a COMPLETE Recovery (if you have the Online Redo Logs). However, an OPEN RESETLOGS is still required. The %r in the log_archive_format since 10g allows ArchiveLogs to be retained through ResetLogs.
If the control keeps track of redo logs SCN, Archive logs history and RMAN backups when these change then wouldn't another control file backup/ trace need to be done ? If you RESTORE the controlfile you lose no information. However, you still have to OPEN RESETLOGS.
If you do a CREATE CONTROLFILE, yes, you lose information about ArchiveLogs history and RMAN Backups.
You can issue a CATALOG command to re-catalog available Backups.
Control File Trace only alllows to rebuild the database not to copy.A Control File Trace is to recreate the Controlfile. Not rebuild the database.
Backup to the Flash Recovery is another backup not an updated copy to copy from but to restore/recovery with. I don't understand what your statement or question might be here.
Hemant K Chitale
http://hemantoracledba.blogspot.com
Edited by: Hemant K Chitale on Mar 2, 2011 2:44 PM
Edited by: Hemant K Chitale on Mar 2, 2011 2:45 PM