Re: Online backup: Backup online redologs?

From: Charles Fisher <Charles.Fisher_at_alcoa.com>
Date: Tue, 08 May 2001 21:38:45 GMT
Message-ID: <Pine.GSO.4.31.0105081630240.1019-100000@unknown>

On Wed, 2 May 2001, Howard J. Rogers wrote:

> > ...but assuming that I am willing to endure the lesser
> > quality, how are the redologs recreated?

> I may be wrong, and I don't have a database to hand on which to test this
> out, but since the commands to create or drop redo logs are all variations
> on a theme of 'alter database', I would have thought that they can be issued
> in the mount stage -which means you can take your binary version of the
> control file, created as you just described, get to the mount stage, add two
> new redo log groups, drop all reference to the existing groups, and alter
> database open resetlogs. The trace file method of course relies on the
> (consistent) presence of the existing logs, because the controlfile has to
> gets its SCN from somewhere. Using the binary file, you're just performing
> boring old incomplete recovery because of a gap in your redo stream.
> I wouldn't consider the resulting database a clone, though, because of that
> resetlogs. But your view might differ.
> Alter database add logfile group 3 "blah/blah.rdo' size 1m (repeat for group
> 4)
> Alter database drop logfile group 1 (repeat for group 2)

Hey, this doesn't work.

I have restored everything, but I have no redologs.

I can mount the database, but here is what happens:

$ svrmgrl

Oracle Server Manager Release 3.0.5.0.0 - Production

Oracle8 Enterprise Edition Release 8.0.5.0.0 - Production With the Partitioning and Objects options PL/SQL Release 8.0.5.0.0 - Production

SVRMGR> connect internal
Connected.
SVRMGR> startup mount
ORACLE instance started.

Total System Global Area                         26148952 bytes
Fixed Size                                          49240 bytes
Variable Size                                     5349376 bytes
Database Buffers                                 20480000 bytes
Redo Buffers                                       270336 bytes

Database mounted.
SVRMGR> alter database drop logfile group 1; Statement processed.
SVRMGR> alter database drop logfile group 2; Statement processed.
SVRMGR> alter database drop logfile group 3; Statement processed.
SVRMGR> alter database drop logfile group 4; Statement processed.
SVRMGR> alter database drop logfile group 5; alter database drop logfile group 5
*
ORA-01567: dropping log 5 would leave less than 2 log files in thread 1 ORA-00312: online log 5 thread 1:
'/pkg/prdcrm/oradata/prdcrm/redoprdcrm05.log' SVRMGR> alter database add logfile group 1

'/pkg/prdcrm/oradata/prdcrm/redoprdcrm01.log' size 10M; Statement processed.
SVRMGR> alter database drop logfile group 5; Statement processed.
SVRMGR> alter database add logfile group 2

'/pkg/prdcrm/oradata/prdcrm/redoprdcrm02.log' size 10M; Statement processed.
SVRMGR> alter database drop logfile group 6; alter database drop logfile group 6
*
ORA-01623: log 6 is current log for thread 1 - cannot drop ORA-00312: online log 6 thread 1:
'/pkg/prdcrm/oradata/prdcrm/redoprdcrm06.log'

Of course, I cannot force a log switch in this state.

What do I do? Using the hotbackup online redologs seems to be the ONLY way to do a complete recovery. If I couldn't get the online redologs for whatever reason, I couldn't recover the database!

Charles J. Fisher - Consultant
Alcoa Davenport Works
(319) 459-2512 Received on Tue May 08 2001 - 16:38:45 CDT