large sga or not,your experience--Re: buffer cache -once again,

Hi,

        Many professionals like Jonathan Lewis(From metalink note, sorry I forget that link) quote

    It __IS__ possible to make things worse by increasing the     buffer to extreme levels. For example, you may allow     Oracle to keep more CR copies of blocks that have been     updated - this will tend to make the hash chains that     need to be searched much longer, and therefore increase     the contention on the cache buffers chains latch.

    And Craig A. Shallahamer's paper:http://www.orapub.com/cgi/genesis.cgi?p1=sub&p2=abs136, it also says large sga can give bad performance.      So , according your experience, what about your sga size with huge amount of physical memory? My personal experience of setup a 13G sga on 16G memory machine is pretty good till now.Physical reads dropped to 1/2 compared to the physical reads when sga is 8G.

Regards
zhu chao
msn:chao_ping_at_163.com
www.cnoug.org(China Oracle User Group)
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Tuesday, May 06, 2003 10:12 PM

> Arvind
> What makes you suspect you've configured your buffer cache too large? A
> better question might be "how can I tell if my buffer cache is properly
> sized?". Start by checking your wait times. What are your top 3 waits? Also,
> what is your (cough, cough) average buffer hit ratio?
>
> Dennis Williams
> DBA, 60%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Tuesday, May 06, 2003 4:37 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Dear All,
>
> how can i check if my buffer cache is bigger than necessary ?oracle db
> version is 8.1.7.
>
>
> Thanks
>
>
> Arvind
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Arvind Kumar
> INET: arvindk_at_sqlstarintl.com
>

>

>
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: zhu chao
  INET: chao_ping_at_vip.163.com

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