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Re: db_block_lru_latches

From: Richard Foote <Richard.Foote_at_oracle.com>
Date: Thu, 08 Aug 2002 17:24:40 +1000
Message-ID: <3D521CB8.6E382E57@oracle.com>


But you need to consider to which pools the latches will be assigned to. Simply setting the db_block_lru_latches to the max may not have the desired effect if you have multiple pools. You need to consider how many of these latches get assigned to each pool. For example, if you have a recycle pool and providing appropriate objects are assigned to it, most contention is likely to occur here, hence it might be more deserving of a greater proportion of latches.

I kinda like the 9i solution where this parameter is now undocumented, presumably because there are now so many different and dynamic caches that manually tuning them could give one a real headache.

Cheers

Richard
Nuno Souto wrote:
>
> daud11_at_hotmail.com (Daud) wrote in message news:<f0bf3cc3.0207300540.3e88d45_at_posting.google.com>...
> > From oracle documentation, it says that using the default value (1??)
> > for db_block_lru_latches may not be good enough especially when # of
> > db writers is set to more than 1.
>
> True.
>
> > My question is will it be ok to just
> > set it to the maximum which is # of cpu x 2 x 3? Any impact on the
> > performance setting it to the max?
>
> I'd say go for it. I've never found any major impact in performance
> by setting them to the recommended upper limit. It's maybe measurable,
> but not major by any means. Set them to calculated max according to manual
> and forget about contention for them in the future. One less problem to
> worry about. You may incur a slight overhead in searching for a latch,
> but we're talking the diff between scanning 8 or scanning 24 in a linear
> list. Hardly the stuff that makes me lose sleep with today's hardware.
>
> >The value of db_block_buffers is
> > 100,000.
>
> Yikes! Unless you're running some third party app with a weird behaviour,
> that's way too high. I've found 20000 seems to be the sweet spot for
> most apps nowadays. And I find it's more influenced by the nature of the app
> and the number of concurrent users than by size of db.
> Of course the "SAPeans" here will disagree with me and allocate at least
> 8 Gb of buffers. Then again, who cares? Mem is cheap, never mind if you
> never use it... ;-)
>
> Cheers
> Nuno Souto
> nsouto_at_optushome.com.au.nospam


Received on Thu Aug 08 2002 - 02:24:40 CDT

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