| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
 |
 | |||
| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
|
| |||
Home -> Community -> Mailing Lists -> Oracle-L -> RE: negative value for buffer cache hit ratio
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..
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: K Gopalakrishnan INET: kaygopal_at_yahoo.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 - 09:03:36 CDT
 |
 |