Re: State of data over the time

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:999809618.13730.0.nnrp-08.9e984b29_at_news.demon.co.uk...
>
> The performance impact is minimal only if you don't use it.
> Rule of thumb:
> Rolling back for read consistency is always expensive.
> Rolling back more than a short distance is extremely expensive.

You're right of course: I should have been more careful in my phrasing. What I meant by saying performance impact was minimal was that the mere act of retaining rollback is not a performance crippler in the way that firing off DML triggers or having to do double-inserts into versioning tables (as I saw suggested by others) would have been. Moreover, flashback merely retains additional undo... it doesn't cause more to be generated for a given transaction than before.

In other words: yes, his *reporting* on the state of data X days ago will be expensive, but his current and continuing DML on the table will progress unhindered and unimpeded.

Regards
HJR
> (Mind you - my first thought was "you could have fun with
> flashback for this one")
>
>
> --
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> Host to The Co-Operative Oracle Users' FAQ
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> Howard J. Rogers wrote in message <3b97dd9d_at_news.iprimus.com.au>...
> >
> >It's part of the database engine, so there are minimal performance
impacts,
> >and Flashback is read only, so there are no worries about database
> >integrity.
> >
>
>
>
>
>
Received on Thu Sep 06 2001 - 19:03:25 CDT