RE: negative value for buffer cache hit ratio

Kirti, Audrey,
I was under the impression that negative numbers are caused by the numbers wrapping around i.e., the database has been up for a while and the statistics pile up and eventually exceed the defined format (e.g. value of 1000+ for a format of 9(3) - to use old COBOL representation !). Makes sense ?
I have seen his before. If you bounce the database, all will be well ! Srini Chavali
Oracle DBA
Cummins Inc

"Deshpande, Kirti" <kirti.deshpande_at_verizon.com>@fatcity.com on 08/07/2001 01:13:52 PM

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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:andreyb_at_elrontelesoft.com]
> 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
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> Author: Andrey Bronfin
> INET: andreyb_at_elrontelesoft.com
>
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Author: Deshpande, Kirti
  INET: kirti.deshpande_at_verizon.com

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Author: 
  INET: Srini.Chavali_at_Cummins.com

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