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Home -> Community -> Mailing Lists -> Oracle-L -> RE: negative value for buffer cache hit ratio
Thanks Rachel good point.
:-)
Ramón Estévez
com.banilejas_at_codetel.net.do
-----Mensaje original-----
De: root_at_fatcity.com [mailto:root_at_fatcity.com]En nombre de Rachel
Carmichael
Enviado el: Wednesday, 08 August, 2001 12:25 PM
Para: Multiple recipients of list ORACLE-L
Asunto: RE: negative value for buffer cache hit ratio
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" <com.banilejas_at_codetel.net.do>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>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
>com.banilejas_at_codetel.net.do
>
>
>
>
>
>-----Mensaje original-----
>De: root_at_fatcity.com [mailto:root_at_fatcity.com]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 <com.banilejas_at_codetel.net.do>
>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
> > com.banilejas_at_codetel.net.do
> >
> >
>
>
>=====
>Have a nice day !!
>------------------------------------------------------------
>Best Regards,
>K Gopalakrishnan,
>Bangalore, INDIA.
>
>__________________________________________________
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>--
>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: K Gopalakrishnan
> INET: kaygopal_at_yahoo.com
>
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>Author: Ramon Estevez
> INET: com.banilejas_at_codetel.net.do
>
>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
>San Diego, California -- Public Internet access / Mailing Lists
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Rachel Carmichael INET: carmichr_at_hotmail.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Ramon Estevez INET: com.banilejas_at_codetel.net.do Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Wed Aug 08 2001 - 13:39:20 CDT
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