Re: re-indexing per statement or per row?

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:1018275095.8506.0.nnrp-12.9e984b29_at_news.demon.co.uk...
>
> It's telling you that Oracle can generate one undo record
> per block modified, and doesn't always generate one undo
> record per row modified.

just musing/nitpicking but should that read one undo record per block modified per statement?

This opens up a whole interesting can of worms for me because I *know* (cos the docs and folk like Howard have told me so) that *in backup mode* that redo is generated for the whole block rather than the modified record(s) (assuming archivelog mode). Yet this is leading to a suggestion that redo *can* be in someways a snapshot of block level changes. which raises the question of how ordinary redo differs from *backup* redo.

And I guess to answer that one needs to know the structure and content of undo records - hmmm deeper knowledge is clearly to be had.(and almost certainly version specific).

>
> Which means that when you have a statement that inserts
> multiple rows, the index can have multiple rows modified
> in one atomic block change - i.e. the index isn't necessarily
> modified one row at a time.

Point taken.

All in all a wholehearted thanks for your thought for the day far more worthwhile than the anodyne pap on Radio4 under the same name. I for one would appreciate more as and when it seems appropriate.

meanwhile my head hurts so I'll find some more beer - thats bound to help <g>.

--
Niall Litchfield
Oracle DBA
Audit Commission UK