RE: Re: quick suggestions for tuning ?

>Jared,
>
>LIO being high and BHCR ~ 99% : is this is a normal
>or abnormal ?
>
>Regards,
>Jp.
>
>12-08-2003 00:44:23, Jared Still
><jkstill_at_cybcon.com> wrote:
>>But his BCHR is 99.57% !
>
>

OK, let's have another try at it. Let's say that you are a travelling salesman, with a number of prospects to visit at a number of locations. Obviously, you may say take your list of prospects and visit them in say alphabetical order. No need to be very clever to guess that, if this is how you proceed, you are going to have a rather impressive mileage. If you have any common sense, you are going to try to see which prospect is close to which other one and, assuming no other constraint about the availability of the people you wan to meet, you are going to see your propects by geographical clusters. In the end, you will have seen the same people than as if you take the list alphabetically. But your mileage will be much, much less. Quite obviously you have to pour fuel in your car. Everytime you stop at a pump, you have delays, because of queues (many cars, not many fuel stations in this area), cashiers, when you have to pay, all seem incredibly lazy and more eager to serve coffee to other customers than let you pay, and you are quite irritated by this because each time you waste a _lot_ of time. Let's say that you take the stupid approach. One way to finish your circuit faster is to say 'hey, I have a *great* idea, I am going to borrow my brother-in-law's car which has a tank twice as big as my car and as efficient an engine. This way I shall spend twice less time on refuelling and it will be faster'. Of course it will. But not necessarily much. Obviously, you should try to minimise the mileage first - necessarily, you'll pay fewer visits to the pump and in fact, you may even not bothering using a car with a smaller tank if you have dramatically decreased the mileage.

Logical I/Os are your mileage, and physical I/Os are the same as refuelling. Increasing the size of your SGA is taking a car with a bigger tank. And computing statistics is knowing the distance between the various locations you want to visit - enabling the optimiser to compute a suitable route. The BCHR is the number of miles you do per refuelling - says something about the quality of the engine but otherwise mostly irrelevant.

Regards,

Stephane Faroult
Oriole

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Author: Stephane Faroult
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