Oracle-L: RE: Order of Redo log use

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Thu, 20 Feb 2003 11:47:42 -0800
Message-ID: <F001.00553573.20030220114742@fatcity.com>

Michael

The reason to use multiple members in each group is so each member can be on a different device (that is device, not just a separate mount point on the same device). Then if a terrorist sprays your computer room with automatic gunfire (or a drive crashes), maybe one of the devices will be spared. Remember that Oracle can easily rebuild data files. Redo logs and control files are the precious commodity. While you are at it, make sure you have two control files on separate devices. I am paranoid so I always configure three control files.

So you need to relocate the second member of each redo log group so both aren't on the same device. Make sure they are all the same size. Evaluate whether you need to make them larger while you are at it. How often does log file switch occur during peak load?

Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Thursday, February 20, 2003 12:34 PM To: Multiple recipients of list ORACLE-L

Ok, I'm working on a 8.1.7 Tru64 system with 10 groups of redo logs with 2 members; 5 groups on each of 2 mount points. I've finally taken a close look at the order each group is used and I'm not happy. Four of the 10 switches are between redo logs on the same mount point. Now I'm not sure when this happened since this database has been around for many years and the number of groups and the size of the redos have increased, and the 2nd members were added. Now I have down time to correct this over the weekend. I know I can just leave the order the groups are used as is and move/rename the underlying redo logs, but I'd rather have all of the even-numbered groups on one mount point and the odd groups on the other. So is this as easy as dropping (except for the active one) and recreated in the order I want them used or is there other factors. For that matter, when new groups are added how are they merged into the order groups are used. Another few points I found is that the default order of group# in V$LOGFILE does not correspond to the order used, and RESETLOGS does not affect the order of group used either. If this is a RTMF let me know that too.

Thanks,
Mike Hand
Polaroid Corp

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Author: Hand, Michael T
INET: HANDM_at_polaroid.com

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Author: DENNIS WILLIAMS
INET: DWILLIAMS_at_LIFETOUCH.COM

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