I'm theorising here..
It may well be version related... I know in 8.1.7.0
they've zero'd out a few of the figures in this view
(possibly due to bugs in the way they were calculated
in versions previous)
I'm on 8.1.7.1 and the figures seem fine to date...
hth
connor
- Djordje Jankovic <djankovic_at_corp.attcanada.ca>
wrote: > 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
> --
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> Author: Djordje Jankovic
> INET: djankovic_at_corp.attcanada.ca
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Received on Thu Apr 05 2001 - 05:32:12 CDT
