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Re: Buffer cache hit very low...!!!

From: Michael McMullen <>
Date: Wed, 14 Sep 2005 09:45:54 -0400
Message-ID: <BAY103-DAV1016ED0123AEF3ECE55710A69F0@phx.gbl>

Well, I did ask for platform. And a 40Gb database on windows 2000 SE, how many people have those? large batch jobs running, small buffer cache. my advice is just as good as telling him to get some books. and the rest of my email did explain how i did tune(by analyzing) a statement that would have had a very high BCHR into one that ran faster but would have had a very low BCHR.
I also stated that increasing to 2Gb would stop the OEM people from bugging him. I guess I could have put smileys everywhere but I leave that for the kids.
Also, the db_cache_size is there for a reason. At some point size matters, I always go for making it big and then forgetting about it. Rather than small and wondering if i should enlarge it by how much. Now that last statement could really use some smileys. ----- Original Message -----
From: "Jared Still" <>
To: <>
Cc: <>; <> Sent: Wednesday, September 14, 2005 9:35 AM Subject: Re: Buffer cache hit very low...!!!

On 9/14/05, Michael McMullen <> wrote:

> 40 Gb database with a 250Mb SGA. What is your db_cache_size? What are you
> running on? I would crank that db_cache_size somewhere close to 2Gb and
> never worry about it again.

That is not good advice considering you don't know anything about the system or the application.

Try 'cranking' your db_cache_size up to 2 Gig on Windows 2000 SE with 4 gig of RAM and watch what happens.

> Yes DBCHR is kind of useless if your cache is
> already large but it would be valid if your cache is too small.

How would this make DBCHR valid?

Will it the DBCHR indicate which SQL statement will is in need of tuning?

Or if your cache is just too small?

Please provide examples.

Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
11+ years of trying to appear to know what I'm doing.
Received on Wed Sep 14 2005 - 08:47:58 CDT

Original text of this message