Re: question about automatic undo management

"Joel Garry" <joel-garry_at_home.com> wrote in message
> Consider a humongous DW combined with a humongous transactional labor
> and inventory system with humongous RBS's and product planners running
> humongous part and labor allocation what-if scenarios for building
> jumbo-jets on it. For each what-if, when they are done, they
> flashback. At some point, they are doing so much undo I/O, it becomes
> substantially like the old contention problems.
>

Sorry Joel: I don't buy this. Flashback means 'show me my table data as it used to be'. The essence of what-iffing (is that a word? Well, it is now!) is that you don't monkey around with the real data, but subset it into some sort of temporary holding area, and do your monkeying around there. When the model comes out not to your satisfaction, dispose of it... there's no rolling back there.

I've done modelling with global temporary tables (8i and 9i), and of course the prize whatiffing strategy must go to Workspace Management (9i only). Either way, undo is generated, it's true, but I don't see either strategy *necessarily* straining undo I/O. And if large amount of undo are generated, and that starts becoming an I/O problem, then configure more undo tablespace datafiles and stripe them across more hard disks.

Regards
HJR
> jg
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Received on Wed Jan 22 2003 - 23:41:33 CST