Re: Re: Re: Configuring Oracle on RAID 5

Your redo log script - posted elsewhere - looks like a script written for Version 6 of Oracle. Unless you have some documentation explaining what it does and why the answer means anything you shouldn't depend on it. (In fact, it is probably telling you that the number of redo copy latch (willing to wait) misses is high relative to the number of redo copy latch (willing to wait) gets is high. This is almost invariably not a problem - look at the actual numbers to check.

In the same vein, any scripts you have which return meaningless numbers without explanation are suspect. Always look at underlying, and related, figures to determine is a simple number is revealing a real problem. For example, if v$waitstat is showing undo header waits (as a source of your 'rollback contention' is the number really significant given the amount of work the database is doing. 500 waits 20 minutes after startup is probably very bad, 500 waits 20 days after startup is probably very good.

For the record - I'm also one of those people that don't reach for the garlic when RAID-5 is mentioned. It does underperform on writes, but not so dramatically that it will destroy the typical small to medium-sized office system. The biggest problem is usually too few spindles rather than the actual RAID choice per se.

However, if you are looking at a really big system, then you have much more scope in choice of disks which may make thinking about RAID-5 irrelevant.

--
Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Practical Oracle 8i:  Building Efficient Databases
Publishers:  Addison-Wesley

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"Anurag Minocha" wrote in message ...


>Writes are not all that important in our system because we run a batch

>process nightly to update the database. The users use the database mainly

>for querying from the web site.

>

>When I run performance tuning scripts it shows me that there is a reo log

>contention of 77% and more. Also there is a contention for rollback undo

>header. Do I need to seriously take a look in these issues or can i ignore

>them because of the fact that the read speed is what that counts and not

 the


>write speed.

>

>Please suggest.

>

>Also let me tell you that we have 2 logical partitions across the same set

>of drives and the database is on the D partition. (All of it).

>

>Thanks

>Anurag

>

>

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