Re: fragmentation - a myth?

benkrug_at_my-dejanews.com wrote:
> Has anyone out there done tests to check the
> effect of fragmentation on performance?
>

Heaps. Long before it was such a "token of knowledge to discuss" topic. Since V6, never found table frag to be relevant (less than 10% improvement in worst case). Index frag IS relevant.

> I wonder whether worrying about fragmentation
> is over-rated. Sure, if you have an old,
> fragmented table/index, and you rebuild them,
> performance is better. But how much of that
> is due to the index rebuild?
>

Sure is over-rated. Since V6.
Most due to index re-build. In 99% of the cases. Table frag is not worth a mention nowadays except in some (very) abnormal cases.

>
> I know theoretically you reduce head
> movement, etc, but I wonder how much that
> matters these days.
>

Not much really, when we consider that many sites out there are using some form of RAID controller or controllers with huge cache memories, as well as huge SGA's... However, index de-frag can be worth it even with this monster hardware.

--
Cheers
Nuno Souto
D.C.S. P/L
e-mail: nsouto_at_acay.com.au Received on Wed Nov 18 1998 - 07:32:12 CST