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RE: Normalization

From: Powell, Mark D <>
Date: Fri, 30 Jul 2004 09:28:27 -0400
Message-ID: <>

My IBM DB2 UDB manuals recommend you normalize all designs to 4th normal form. If you must denormalize you go down to 3rd normal form. Denormalizing usually creates more problems than if fixes. The real problem is that most designers/developers cannot even design to 3rd normal form correctly.

IMHO -- Mark D Powell --

-----Original Message-----
[]On Behalf Of Niall Litchfield Sent: Friday, July 30, 2004 4:17 AM
Subject: Re: Normalization

Dear Bill

On Thu, 29 Jul 2004 12:09:23 -0600, Bill Sable <> wrote:
> I recall a quotation to the effect that no database will perform
> in 3rd Normal Form. To me this defines the difference between theory and
> reality. I have had the 'pleasure' to deal with 2 separate
> that were exact copies of the OLTP structures. They work fine for a few
> months, then performance *rapidly* degrades to the point where the system
> basically useless.

As I think others have said, designing for a true DW situation may well involve a different set of disciplines than OLTP design. (Of course it may not). If a DW system really is an exact copy of the online system, then I'd be very tempted to ask why it was being built. If the OLTP system can already meet all your reporting needs in an adequate way why build a new system - if you really need to offload work to some other server then standby or even that three letter acronym beginning with R might be appropriate.

I've always thought, been taught, that you design for OLTP etc in 3NF, you then (in an unsurprisingly close model of the hotsos tuning approach) see how the critical business processes perform, and if they don't meet your requirements then and only then do you denormalize, and you stop denormalizing when your code performs to spec.

I have to confess I haven't seen many systems like this, so maybe the original suggestion is closer to current business practice.

Niall Litchfield
Oracle DBA

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Received on Fri Jul 30 2004 - 08:27:51 CDT

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