Re: high db hit ratio and a lot of waits on db sequential reads

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

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LSC



On 9/25/07, genegurevich_at_discover.com <genegurevich_at_discover.com> 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

>

>

> --

> http://www.freelists.org/webpage/oracle-l

>

>

>


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