> > Checking in late on this one but my reaction to what Mr. Millsap is saying
> > is basically "Well duh!"
> > It is like putting a program into a loop and watching the CPU race and
> > thinking that that means you have a very efficient program. It seems rather
> > obvious that hit ratio, as an isolated metric, is rather meaningless.

> > Also, there is that old adage, "If it is too good to be true, it probably
> > is." Well, 99% is too good to be true so it is very suspicious and I think
> > Mr. Millsap is saying that the number one suspect would be a badly tuned SQL
> > statement.

> > So, if the hit ratio is fairly low, and you know your SQL is well tuned,
> > then throwing more RAM at the problem is probably a good idea. Right?

> > But this raises some questions in my mind that some of the gurus in here may
> > like to comment on.

> > "When is a PHYSICAL IO NOT A Physical IO? and does it matter?"
> > I am thinking about RAM disk cache here, and RAID and any other type of
> > physical device that may look like a physical IO to Oracle but may not be
> > requiring an actual disk read. And then there is the problem of other
> > applications running on the same system that may be determining if Oracle's
> > request for a physical IO can be serviced by a Logical IO at the OS/device
> > level.

> > Goodbye science, hello art.

> > Mike

> ><snipped>

> Not claiming guru status but I'll give you my opinion:

> If it ain't broke don't fix it. By which I mean that there enough
> real problems in any database application that developers and DBAs
> should be focusing on those before worrying about hit ratios and
> whether an IO is or is not truly a physical IO.

> I've yet to see the database application where such esoteric issues
> where the root cause of the problem. Concentrate on the low hanging
> fruit ... indexes, bind variables, explain plan, autotrace, and hold
> code reviews and you'll likely never have to care.

> Which doesn't mean the topic isn't important but rather the point out
> that too often people get hung up on the esoteric and don't deal with
> the all too obvious.