"Noel" <tbal_at_go2.pl> wrote in message
news:ec30e927.0311210141.3369e057_at_posting.google.com...
> "Anurag Varma" <avdbi_at_hotmail.com> wrote in message
news:<yDfvb.529$Sm1.65_at_news02.roc.ny>...
> > "Geomancer" <pharfromhome_at_hotmail.com> wrote in message
news:cf90fb89.0311201853.126b1516_at_posting.google.com...
> >
> > He does not say that 99.9% hit ratio is always bad (which you seem to be
interpreting).
> > However he does seem to be saying one should NOT rely on 99.9% hit ratio
to make the judgment that
> > the database performance is good. The fact might just be the opposite.
>
> Not hard to imagine bad sql query slowing the database performance.
> Hit ratio hides number of memory/disk reads.
> If you would load all datafiles into memory and database buffers the
> hit ratio would always be 100%.
Not true. Trivially because there always has to be an initial read, less
trivially because dirty blocks get written down to disk and reread. Oracle
isn't an in-memory database.
--
Niall Litchfield
Oracle DBA
Audit Commission UK
Received on Fri Nov 21 2003 - 06:59:05 CST
