Re: Oracle Performance -- Possible Disk Bottleneck

On Jun 21, 9:22 am, beth.sto..._at_gmail.com wrote:

>
> Thanks so much to everyone who replied. It seems apparant that we do
> have a disk bottleneck here. The question is why are there so many
> reads on the database.
>
> I disabled AV scanning, and this didn't improve things -- reads are
> still way high. They peak at 8000 Reads/sec during busy times.
>
> I went through the Metalink article, and we are beginning to identify
> some "hotspots." The DBA was aware of a problem with a particular
> table, and this showed up at the top of the list, so we'll start
> looking there.

If you are aware of particular tables or indices that have problems, you may have some luck examining v$bh and creating multiple buffer pools - see http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96533/memory.htm#30936 . This doesn't necessarily fix the root problem, but it may reduce unnecessary thrashing in the default pool due to those objects. "Unnecessary thrashing" means it is asking too often for things from disk. I've only used a recycle pool, for my particular situations it has been quite helpful. Some people find it hard to get their head around the concept that a warm segment can have such an effect on other processes' hot blocks, though this fits with what Jonathan mentioned about concurrent tablescans.

>
> "Choose" mode will be implemented in new version of the application
> which will be installed later this summer. Optimization modes have
> caused problems before, so hopefully this will fix those issues.
>
> There are plans to upgrade to 10g in the not-so-near future. The
> vendor is testing that, and we're doing testing of our own.
>
> We're also looking at giving the LUN more spindles. We'd like to
> avoid doing this if possible because of the cost.
>
> Thanks again for your help. I've been very impressed with this group
> and its willingness to help out.

jg

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