Re: optimal size for rollback

Hi Niall,

Yes, I noticed Connor's comments and that's why I didn't say I hadn't say 'any' :)

Actually, I'm a fence sitter here as well (hell fence sitting is my middle name).

If you can manually tune these mammas as Howard has mentioned (and if you can tune them without any fear of the age old shrinkage problem where all know and love so well) then that's preferable.

But there's a cost. You need the time and skill to set this appropriately. You need potentially more disk, you potentially need more time for monitoring and tuning.

By using optimal (appropriately) or by using USM, you simplify administration (maybe), you reduce disk storage (maybe) but there's a cost. Potentially performance is impacted.

So what's the correct answer. Well my view is that there isn't necessary the one correct answer. If you've looked on both sides of the fence and you go down a educated path where you pick the solution or the methodology that's appropriate for your environment, and the cost trade-off whatever they might be are recognised and something you're willing to pay, then you've done your job.

Your's balancing as ever ...

Richard
"Niall Litchfield" <niall.litchfield_at_dial.pipex.com> wrote in message news:3d8dfbff$0$8514$cc9e4d1f_at_news.dial.pipex.com...
> "Richard Foote" <richard.foote_at_bigpond.com> wrote in message
> news:q9jj9.37911$g9.108570_at_newsfeeds.bigpond.com...
> > Hi Howard and Karen,
>
> > One last point. Note that automatic undo management does extra work
'under
> > the covers' which could be viewed as being sub-optimal. I haven't heard
> many
> > that suggest using manual rollback segments is the way to go in 9i ...
>
> Connor certainly suggested that automatic undo management was
>
> 'basically an OPTIMAL clause
> just under the covers...Its like "Oops, I'm an extent thats 3 seconds
> over the retention limit...bang, I'm outta here"'
>
> which isn't exactly a ringing endorsement...
>
> And I must admit I am still sitting on the fence, at least partly because
I
> don't really understand what AUM is actually doing, and partly because
> sufficient equisized public rollback segments have never done me any
> significant harm. Sizing them wrong or leaving a big or small rbs segment
> online when I didn't intend to on the other hand.
>
>
> --
> Niall Litchfield
> Oracle DBA
> Audit Commission UK
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Received on Sun Sep 22 2002 - 17:16:25 CDT