I have been following your blogs very regularly and they have always been very insightful. Offlate we have a debate going on internally withing a bunch of DB professionals and we are trying to identify what exactly drives organizations to migrate from one DB to another. In this one of the DB2 professional sent me a link:

http://www.gartner.com/resources/167700/167786/ibm_db2_97_shakes_up_the_dbm_167786.pdf

and it really appalled me to see that a huge org like IBM is adopting a startegy to go after Oracle rather than come with something good of their own.

I have just started reading your book Oracle Core… and I think chapter 02 should really end this debate.
What are your thoughts?

Note: My apologies if I have posted this in the wrong place…but I could not really find a right post to put this query through

Regards,
Vikram R

The example that Richard gives in that article is demonstrating a particular special case – if you delete and reinsert a unique key (protected by a unique index) within the single transaction, the index entry is marked as deleted, and then the delete flag is cleared so the index entry is immediately re-used.

In the more general case, if your transaction deletes one index entry from a unique index and inserts a different value (and it’s one that is so close to the original that it should go in the same block) then the space from the deleted entry will not be available for reuse.