Re: DB2 HADB

"Mark A" <nobody_at_nowhere.com> wrote in message news:z5udnftJ7ZzZDxrenZ2dnUVZ_sCdnZ2d_at_comcast.com...
>
> The main reason is that DB2 has table clustering, which Oracle does not
> have unless you use an index ordered table (which maintains the data in
> exact order all of the time like an index, and is can be a bit
> time-consuming for inserts due to the extra work involved).
>
> DB2 clustering only "tries" to insert the row on the correct page (never
> rearranges rows on the page like an index), and if the correct page or a
> nearby page is not available, then it doesn't waste time with page splits
> (just puts the row anywhere). The area on a page used for inserting new
> rows is different on Oracle compared to DB2, and a reorg restores the free
> space percent (as specified when the table is created) on each page for
> new inserts in when a clustering index is defined.
>
> DB2 table clustering is not "needed", and it is optional, but in many
> cases it does provide a definite performance enhancement with the extra
> overhead of an index ordered table in Oracle. Since DB2 has true on-line
> reorgs, there is no downtime, so I don't know it bothers you so much.
>

Correction:

it does provide a definite performance enhancement WITHOUT the extra overhead
of an index ordered table in Oracle. Received on Fri Nov 25 2005 - 16:48:00 CST