Re: Oracle slowed down

"HansF" <News.Hans_at_telus.net> wrote in message news:pan.2006.04.21.02.14.20.634587_at_telus.net...
> On Fri, 21 Apr 2006 02:33:53 +0000, Bob Jones wrote:
>
>
>>
>> May I aslo suggest reading Oracle's official performance tuning books?
>
> In which they discuss the ratios as an indicator of buffer cache size
> issues - to be used when statement, application, I/O and system tuning
> have been completed. Unfortunately many people skip over the 'yes but'
> part.
>

On the other hand, if the buffer cache is too small for the amount of data your are dealing with, everything else can be tune to perfection, the performance will still be poor.

> Bottom line - BCHR calcs can be caused to show just about any value one
> wishes. There are a number of sites and books (as indicated) that show
> how you can generate virtually any BCHR without changing anything in the
> system.
>

Sure, you can artificially obscure the hit ratios, but that does not make hit ratio irrelevant in a real production enviornment. If hit ratio is meaningless, there would be no need to tune buffers.

> A good BCHR may be the result of very, very poorly written tablescanner.

I am not sure what you mean here.

> So the novice DBA and developer feel great that they have achieved the
> best possible performance for a piece of crappy code. Similar to putting
> in wait loops into C and tuning the heck out of the call stack.
>

That is really a different issue. Application tuning and buffer tuning are two separate things. They are both relevant to the performance. Received on Thu Apr 20 2006 - 22:21:28 CDT