Re: separate data/inidex

In article <1020584466.4135.0.nnrp-08.9e984b29_at_news.demon.co.uk>, you said (and I quote):
>
> Can either of you explain your comment about
> defragmenting discs.
>
> Since a typical Oracle installation creates its
> data file just once and never deleted, moves
> or extends/shrinks them, your comment
> tends to suggest that NT updates a block
> within a file by copying it do a different
> location on the disc and redirecting the
> directory map. Surely that can't be true !
>

Good point, Jonathan. NTFS can be very brain-dead when it comes to placing file fragments (sectors). This is at file creation time, not dynamic as usage goes by.
What happens in a nutshell(won't go into all details here, not enough space):

• You create your initial files. NTFS will still fragment them around the MFT even though you are working off a pristine freshly made partition. This because NTFS is completely incapable of creating a contiguous file even when you specify the final size and a single allocation. In fact it uses a strange algorithm to attempt to "optimally" place the file by fragmenting it around the MFT. Even though you know your placement was optimal.
• So, you created your first datafile that is now fragmented even though you asked for it to not be. Then you create the second one, which now NTFS will insist on placing "optimally" by "breaking" it around the already "broken" first file.
• And so on, chain reaction. With half a dozen big files, your data file fragments will be all over the place. Run a good defragger and it will show this problem even on a freshly made disk. Mix up a few other folders with programs or software and you're virtually guaranteed a well fragmented disk. All in the interest of optimisation.

Best thing to do? Create all your data containers and any other folders on the disk. Then defrag.

Do this also anytime you have to drop/create/re-create any big data file on that partition (like when reorg/recovery/adding more disk space), or add/remove folders and their contents. All of these fragment any new stuff as well.

I read somewhere that NTFS may in some instances relocate existing fragments when the disk becomes quite full. One of the "golden rules" of NTFS is to never fill a partition more than 75%. After this strange things happen if you have any part of it be volatile. As in when you share Oracle datafiles and other folders in the same disk. Not sure if this still true in W2K, but it was in early NT4.

-- 
Cheers
Nuno Souto
nsouto_at_optushome.com.au.nospam