Re: Extent Numbers (Was Re: Interview question)

"Frank" <fbortel_at_hotmail.com> wrote in message news:397EDD88.39FD2764_at_hotmail.com...
> >snipped previous discussion>
> > However, in general, fewer extents are good for your data dictionary.
 'Nuff
> > said!
> >
> > How about taking a quick trip to
> > http://www.ixora.com.au/tips/creation/extents.htm for that full
 discussion
> > of the issues you were after? If anyone can contradict Steve's
 findings, I
> > haven't seen them do it.
> Have you??? Qoute from this very page:
>
> It is necessary to dwell on this briefly because some DBAs are reluctant
> to allow more
> than a few extents in any segment in the mistaken belief that
> such "fragmentation" degrades performance.
> This myth was started by the Oracle documentation for the export utility
> in version 3, and is still
> abroad.
>
> What do the words "mistaken" and "myth" tell you?
>
> 'nuff said, indeed. Extents are not bad for performance, allocating them
> 'on-the-fly' is.
>
> Frank

Don't be ridiculous, Frank, please. You have taken a couple of sentences from a very in-depth discussion entirely out of context. Read the *entire* page again, and you will discover (with not a lot of difficulty) that Steve explains precisely why more than half a dozen extents is bad news -it introduces chaining in the data dictionary. Therefore, and as I have repeatedly said, allocation of lots of extents in and of itself is not a direct problem for the table, but performance will nevertheless be adversely affected because of the degradation such allocation will cause on the data dictionary.

Quite how you can read his page and come to a different conclusion, I have no idea. Wishful thinking, I suspect. Which in this case bears no relation to the facts of the matter.

Regards
HJR Received on Thu Jul 27 2000 - 00:00:00 CDT