Re: high db hit ratio and a lot of waits on db sequential reads
- From: "LS Cheng" <exriscer@xxxxxxxxx>
- To: genegurevich@xxxxxxxxxxxx
- Date: Thu, 27 Sep 2007 08:42:12 +0200
Hi
if you have modifications going on then time to time you have to read from
disks somehow, checkpoints flush dirty blocks to disk, then those need to be
read etc etc etc
now, if it's a read only database and your cache is so large that everything
fits in then I dont know...
thanks
--
LSC
On 9/25/07, genegurevich@xxxxxxxxxxxx <genegurevich@xxxxxxxxxxxx> wrote:
>
>
> Hi all:
>
> I am working on tuning an app running against oracle 10.2.0.3 We have 48G
> on the server; my db_cache is 18G. When I
> look at the awr reports, I see db hit ratio being over 99% and a lot of
> waits for db sequential reads. Based on the SQL
> there are a lot of table reads based on the primary keys so that kind of
> waits is reasonable. But the question is
> if the hit ratio is that high , if we read mostly for the cache, why do we
> do that many reads. Is there an explanation for that?
>
> thank you
>
> Gene Gurevich
>
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
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