Hi,
The physical_reads, db_block_gets, consistent_gets fields in
v$buffer_pool_statistics have strange values, so if the Hit ratio is
calculated according to the usual formula the result is
-120. I hope it is not that bad ;-).
For the KEEP pool everything is OK.
Any idea, what is wrong there ? The database has not been so long up for
numbers to wrap around the maximum.
SQL> select name BufferPool
2 , physical_reads, db_block_gets, consistent_gets
3 from sys.v$buffer_pool_statistics
4 /
BUFFERPOOL PHYSICAL_READS DB_BLOCK_GETS CONSISTENT_GETS
-------------------- -------------- ------------- ---------------
KEEP 361 9,953,228 19,849,8415
DEFAULT 2,150,451,312 202,265,542 769,364,625
SQL> select name BufferPool
2 , 100*(1-physical_reads/(db_block_gets+consistent_gets)) HitRatio
3 from sys.v$buffer_pool_statistics
4 /
BUFFERPOOL HITRATIO
-------------------- ----------
KEEP 99.9998269
DEFAULT -120.58298
I have also run Steve Adams's
(http://www.ixora.com.au/scripts/sql/buffer_pool_miss_rates.sql) script and
got the similar weird result:
BUFFER_POOL MISS_RATE
-------------------- ---------
DEFAULT 219.09%
KEEP 0.00%
So, I guess the problem is in the outlining data.
In the v$sysstat the numbers for physical reads, and db block gets are
similar, but the number for the "consistent gets" defers a lot (approx. 60
times). There the hit ratio is not that good but at least makes sense:
column BlockGets format 999,999,999,999 heading "Block Gets"
column ConsGets format 999,999,999,999 heading "Consistent Gets"
column PhysReads format 999,999,999,999 heading "Physical Reads"
column BuffCache format 999.999 heading "Buffer Cache Ratio"
select BlockGets.value BlockGets
, ConsGets.value ConsGets
, PhysReads.value PhysReads
, 100*(1 - PhysReads.value/(BlockGets.value+ConsGets.value))
BuffCache
from v$sysstat BlockGets
, v$sysstat ConsGets
, v$sysstat PhysReads
where BlockGets.name = 'db block gets'
and ConsGets.name = 'consistent gets'
and PhysReads.name = 'physical reads'
/
Block Gets Consistent Gets Physical Reads Buffer Cache Ratio
---------------- ---------------- ---------------- ------------------
235,191,957 12,077,935,459 2,177,467,949 82.316
Thanks.
Djordje Jankovic
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Djordje Jankovic
INET: [EMAIL PROTECTED]
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: [EMAIL PROTECTED] (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).
