> > > Please don't tune by hit ratios!!!!
> > >
> > > They are largely meaningless, as a quick trip to Connor's site
> > > (www.oracledba.co.uk) and the 'Tuning' link will show you: he has a very
> > > nice script there, under the "Custom Hit Ratio" link, which lets you
> dial
> > > your own hit ratio. Fancy 97%.... Lo! it shall be so. 98.5% anyone?? Go
> for
> > > it: the script makes it so.
> >
> > I have to respectfully disagree. Even something similar to the script
> > were part of your normal system activity, the hit ratio is still
> > meaningful. But it is about as uncommon as gauging mpg with a fast
> > leaking gas tank.
>
> It's meaning is that *for the sql that you are running* such and such a
> proportion of the execution plan that was chosen was answered from memory
> not disk. It doesn't however tell you anything about how good the SQL is or
> how good the plan is. Try this thought experiment (or if you are brave try
> it in your office).
>
Hit ratio is not meant to tell how good the SQL is.
Received on Fri Oct 04 2002 - 11:54:45 CDT
