Ramon,
if you find the performance of the database is good, why are you trying to
fix it??????
Cache Hit Ratio is not the be-all and end-all of tuning. If the cache hit
ratio is high, and you have large numbers of wait events, then your database
needs tuning.
If the cache hit ratio is low, but there are no wait events then your
database does not need tuning.
Rachel
>From: "Ramon Estevez" <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
>Subject: RE: negative value for buffer cache hit ratio
>Date: Wed, 08 Aug 2001 06:27:11 -0800
>
>Thanks,
>
>As far as I know, the correct value is as close to 100% as possible.
>So, if mine is 0.68
>
>-------------------------*
>MISS_RATE I
>--------- I
> 0.67% I
> I
>This is now 9:15 am. I
>-------------------------*
>
>I find the performance of the DB good, but as the result of the query
>I think that it could get better.
>
>I executed this script that was posted yesterday in the list.
>
>
>select to_char(100 * misses / (logical - physical + misses), '9990.00')
>||
> 2 '%' miss_rate
> 3 from ( select total_waits misses
> 4 from sys.v_$system_event
> 5 where event = 'db file sequential read'),
> 6 ( select value physical
> 7 from sys.v_$sysstat
> 8 where name = 'physical reads'),
> 9 ( select sum(value) logical
>10 from sys.v_$sysstat
>11 where name like '%consistent read gets'
>12 or name = 'db block gets');
>
>
>
>Ramon Estevez
>[EMAIL PROTECTED]
>
>
>
>
>
>-----Mensaje original-----
>De: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]En nombre de K
>Gopalakrishnan
>Enviado el: Tuesday, 07 August, 2001 5:07 PM
>Para: Multiple recipients of list ORACLE-L
>Asunto: RE: negative value for buffer cache hit ratio
>
>
>Hi,
>
>Generally speaking.. HIT RATIOS does not give the true
>picture always. I have seen databases performing
>extremely good with 50% and bad databases with 99% hit
>ratio.
>
>You should never decide the database performance based
>on hit ratio and 90% hit ratio does not mean that 90%
>of the data is ALWAYS read from the cache. It
>translates in to something like this..A block is read
>(consistent get) 9-10 times before written to disk..
>
>You should check your system wide wait statistics for
>better tuning..
>
>
>
>
>--- Ramon Estevez <[EMAIL PROTECTED]>
>wrote:
> > Hi,
> >
> > My misses is
> >
> > MISS_RATE
> > ---------
> > 0.68%
> >
> > Is that good or bad, Oracle 8.0.5 Standard Edition,
> > Windows 2000.
> >
> > Is there a 8.1.7 Standard Edition Version ?
> >
> > Ramon Estevez
> > [EMAIL PROTECTED]
> >
> >
>
>
>=====
>Have a nice day !!
>------------------------------------------------------------
>Best Regards,
>K Gopalakrishnan,
>Bangalore, INDIA.
>
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