1.- Go to this link of Steve Adam's site:
http://www.ixora.com.au/scripts/cache.htm
You gonna find a script to estimate the miss rate of
the buffer cache based on the assumptions that certain
operations are not well compute by statistics as
direct path operations.
2.- From 8.X you should rely on
v$buffer_pool_statistics from the script
$ORACLE_HOME/rdbms/admin/catperf.sql accounting on the
several pools you could have.
3.- Remember that even on 8.X, when the database has
been opened for a long time and have had a lot of
transactions, the value of statistics gets so big that
reaches the maximum value and then begins from 0
again. This usually happens with 7.X.
Regards.
--- "Deshpande, Kirti" <[EMAIL PROTECTED]>
wrote:
> Andrey,
> I am not into cache hit ratios, but got curious
> about your negative value.
>
> So I casually searched Metalink for 'negative value
> for hit ratio'. And got
> a hit on 'MROC: I am receiving a negative Buffer
> Cache hit ratio' thread.
> You may want to check it out, there seems to be a
> new formula for hit ratio
> computation in 8i/9i.
>
> HTH,
>
> Regards,
>
> - Kirti Deshpande
> Verizon Information Services
> http://www.superpages.com
>
> > -----Original Message-----
> > From: Andrey Bronfin
> [SMTP:[EMAIL PROTECTED]]
> > Sent: Tuesday, August 07, 2001 12:51 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: negative value for buffer cache hit ratio
>
> >
> >
> > Dear gurus !
> > I have a negative value for buffer cache hit ratio
> in my DB which is up
> > for
> > some 4 months .
> > Any ideas why ?
> > Thanks in advance.
> >
> > SQL> SELECT (1 - (SUM(DECODE(a.name,'physical
> reads',value,0)) /
> > 2 (SUM(DECODE(a.name,'consistent
> gets',value,0)) +
> > 3 SUM(DECODE(a.name,'db block
> gets',value,0))))) * 100 "buffer cache
> > hit
> > ratio"
> > 4 FROM v$sysstat a;
> >
> > buffer cache hit ratio
> > ----------------------
> > -52.99284
> >
> > --
> > Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> > --
> > Author: Andrey Bronfin
> > INET: [EMAIL PROTECTED]
> >
> > 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:
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> --
> Author: Deshpande, Kirti
> INET: [EMAIL PROTECTED]
>
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=====
Eng. Christian Trassens
Senior DBA
Systems Engineer
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