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Home -> Community -> Mailing Lists -> Oracle-L -> RE: negative value for buffer cache hit ratio
I assume you have 8.1.7, since 8.1.7 they changed things back to how it was done in 7.3.4.
This script works for 7.3.4 and 8.1.7/9.0.1
select to_char(100 * misses / (logical - physical + misses), '9990.00') ||
'%' miss_rate
from ( select total_waits misses
from sys.v_$system_event
where event = 'db file sequential read'),
( select value physical
from sys.v_$sysstat
where name = 'physical reads'),
( select sum(value) logical
from sys.v_$sysstat
where name like '%consistent read gets'
or name = 'db block gets');
"Do not criticize someone until you walked a mile in their shoes, that way
when you criticize them, you are a mile a way and have their shoes."
Christopher R. Spence OCP MCSE MCP A+ RAPTOR CNA
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275
Fuelspot
73 Princeton Street
North, Chelmsford 01863
-----Original Message-----
Sent: Tuesday, August 07, 2001 3:36 PM
To: Multiple recipients of list ORACLE-L
Ran this query under 8i(HP-UX 11)
SQL> show user
USER is "SYS"
SQL> select to_char(100 * misses / (hits + misses), '9990.00') || '%'
miss_rate
2 from ( select total_waits misses
3 from sys.v_$system_event
4 where event = 'db file sequential read' ),
5 ( select sum(dbbget + conget - pread) hits
6 from sys.x_$kcbwds
7 where inst_id = userenv('Instance') )
8 /
from sys.x_$kcbwds
*
Under 7.3.4.5 (HP-UX 10.20)
SQL> show user
user is "SYS"
SQL> select to_char(100 * misses / (hits + misses), '9990.00') || '%'
miss_rate
2 from ( select total_waits misses
3 from sys.v_$system_event
4 where event = 'db file sequential read' ),
5 ( select sum(dbbget + conget - pread) hits
6 from sys.x_$kcbwds
7 where inst_id = userenv('Instance') )
8 /
where inst_id = userenv('Instance') )
*
So what is wrong?
Regards
MOHAMMAD RAFIQ
Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
Date: Tue, 07 Aug 2001 10:13:51 -0800
Try this more accurate query:
select to_char(100 * misses / (hits + misses), '9990.00') || '%' miss_rate
from ( select total_waits misses
from sys.v_$system_event
where event = 'db file sequential read' ),
( select sum(dbbget + conget - pread) hits
from sys.x_$kcbwds
where inst_id = userenv('Instance') )
/
Also, send the actual values if this query still leads to similar results.
The difference here is it takes in account of direct writes.
"Do not criticize someone until you walked a mile in their shoes, that way
when you criticize them, you are a mile a way and have their shoes."
Christopher R. Spence OCP MCSE MCP A+ RAPTOR CNA
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275
Fuelspot
73 Princeton Street
North, Chelmsford 01863
-----Original Message-----
Sent: Tuesday, August 07, 2001 1:51 PM
To: Multiple recipients of list ORACLE-L
Dear gurus !
I have a negative value for buffer cache hit ratio in my DB which is up for
some 4 months . Any ideas why ? Thanks in advance.
SQL> SELECT (1 - (SUM(DECODE(a.name,'physical reads',value,0)) /
2 (SUM(DECODE(a.name,'consistent gets',value,0)) +
3 SUM(DECODE(a.name,'db block gets',value,0))))) * 100 "buffer cache
hit
ratio"
4 FROM v$sysstat a;
buffer cache hit ratio
-52.99284
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Andrey Bronfin INET: andreyb_at_elrontelesoft.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: Christopher Spence INET: cspence_at_FuelSpot.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). _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Mohammad Rafiq INET: rafiq9857_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: Christopher Spence INET: cspence_at_FuelSpot.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).Received on Tue Aug 07 2001 - 14:28:58 CDT
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