Re: Should I Defragment on RAID?

Hi Bill:

Contrary to some beliefs, the number of extents in a segment is not necessarily equivalent to the level of fragmentation of the segment. See the article on the site below under Performance -> Storage.

If your application is doing a large percentage of full table scans, you should be able to get quite a considerable performance boost by doing some indexing. (We're talking 5, 10, 20, sometimes even 100-200 times faster for individual queries.) AND access by index if immune to table fragmentation (if you define "fragmentation" as scattered empty space within a segment, which, IMHO, is the correct definition).

Good luck,

--
David C. Sisk
Need tech info on Oracle? Visit The Unofficial ORACLE on NT site at http://www.ipass.net/~davesisk/oont.htm Like original music? Listen to song samples and buy a CD at http://www.mp3.com/disparityofcult

Bill Buchan wrote in message <7osb59$ss0$1_at_phys-ma.sol.co.uk>...
>Hi,
>
>I have an Oracle 8.0.4 database on WinNT. The datafiles are all on RAID-5.
>Some of my segments have got seriously fragmented with dozens of extents
all
>over their tablespace. Is it still worth defragmenting these given that
the
>hardware will stripe this data all over the place anyway?
>
>I have a lot of queries that do full scans of the fragmented segments.
>
>Any advice would be much appreciated.
>
>Thanks,
>
>- Bill.
>
>
>
Received on Wed Aug 11 1999 - 22:15:31 CDT