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Re: Wow, Man, Flashbacks!

From: Daniel W. Fink <Daniel.Fink_at_Sun.COM>
Date: Thu, 06 Nov 2003 10:39:25 -0800
Message-ID: <F001.005D5DA1.20031106103925@fatcity.com>


Actually, flashback is available regardless of the undo management configuration. Flashback requires use of the smon_scn_time table, which is populated with an scn -> time relationship every five minutes the instance is up. The table is restricted to a certain size (14400 entries IIRC) by the update logic, so the 5 days of flashback time is a result of the old records being 'aged' off the table.

Using AUM increases the likelihood that a flashback query will succeed, but it is not a guarantee. The logic of block reuse in AUM should increase the retention of undo.

Daniel Fink

Melanie Caffrey wrote:

> Yes, this is correct.
>
> Rollback segments cannot be used.
>
> --- Stephen Andert <StephenAndert_at_firsthealth.com>
> wrote:
> > Bambi,
> >
> > Are you using automatic undo management or manual?
> > I think that
> > flashback can only be used with auto.
> >
> > Stephen
> >
> > >>> bbellow_at_chi.navtech.com 11/06/03 10:04AM >>>
> > Hi Folks!
> >
> > I got waylaid(?) when I got in this morning and
> > these user dudes were
> > talking about using flashbacks, and I was like
> > "Woah! Dudes! Let's
> > just
> > chill on this for a couple of minutes". So, I went
> > back to my desk
> > and
> > checked out a cool article on it...
> >
> >
> http://www.oracle-base.com/Articles/9i/FlashbackQuery.asp
> >
> >
> > And it looks like it's like, killer, yknow? So, I
> > was thinking "well,
> > we've
> > got sufficiently large undo segments for this, I
> > don't see a problem
> > with
> > it" but that didn't sound terribly cool, and anyway,
> > before I go
> > willy-nilly
> > saying this is the niftiest thing Oracle's done in
> > years, I thought I
> > would
> > run it by you guys and see if anybody out there is
> > running with
> > flashbacks
> > and whether there have been any problems with it.
> >
> > Yer far-out pal,
> > Bambi.
> >
> >
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.net
> > --
> > Author: Bellow, Bambi
> > INET: bbellow_at_chi.navtech.com
> >
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> > Author: Stephen Andert
> > INET: StephenAndert_at_firsthealth.com
> >
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> Author: Melanie Caffrey
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>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Daniel W. Fink
  INET: Daniel.Fink_at_Sun.COM

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Received on Thu Nov 06 2003 - 12:39:25 CST

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