Oracle-L: Re: 9i-OCP Question

From: Jonathan Gennick <jonathan_at_gennick.com>
Date: Fri, 01 Aug 2003 19:34:24 -0800
Message-ID: <F001.005C8507.20030801193424@fatcity.com>

Wednesday, July 30, 2003, 1:19:31 PM, you wrote:

Q>> If you have 2 redo log groups with 4 members each, how many disks does
SK> Oracle recommend
SK>    to keep the redo log files?

My first thought was 8, and I think you might be able to make a case for 8. However, you should have at least 4, because the whole reason for multiple members is have copies on separate disks, so the maximum number of members in a group ends up being the minimum number of disks, otherwise you should reduce the number of members.

Does Oracle truly even make a recommendation with respect to this question? Jacques Kilchoer came up with this quote from the manuals:

When setting up a multiplexed online redo log, place members of a group on different disks.

However, this quote does not speak to the total number of disks. It says put each member of a group on a different disk. Ok, fine, but either 4 or 8 disks will meet that recommendation equally well.

It occurs to me though, that the question approaches the issue all backwards. The implication is that you:

first decide how many members you have

secondly decide how many disks to spread those members across

But who thinks like that that? I've always approached things this way:

first I decided how many redundant copies I want of each log file

then I create that many members, each on a separate drive

My point here is that in real life, I don't think I'd ever be asking myself the question Senthil posted from that practice exam.

Best regards,

Jonathan Gennick --- Brighten the corner where you are http://Gennick.com * 906.387.1698 * mailto:jonathan@gennick.com

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Author: Jonathan Gennick
INET: jonathan_at_gennick.com

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