Re: Normalization was Left AS/400 and Returned

Performance will also sufer at other times, which I'm sure
we are aware of.  Keeping indexes up to date isn't "free".
 That takes time to.  Anytime the database is updated,
indexing occurs.

We should just go back to hierarchical database files.
 Hey, we can use XML!  :)

Brad

On Tue, 3 May 2005 13:55:57 -0500
 rob@xxxxxxxxx wrote:
> I agree on the multi-format and join logical files.  Or,
> SQL's views.  And 
> highly recommend them for programming, and, most
> especially, for common 
> links the users use in Queries instead of having them
> join multiple files 
> together.
> 
> However, he might be right about the performance issue.
>  For example, 
> which would access faster:
> 1 - A key over customer number and part number in a
> de-normalized 
> order/line file.
> 2 - A join logical that joins the order/header file with
> the order/line 
> file so that you can see the customer number from the
> order header file at 
> the same time you see the part number of the order line
> file.  And, keep 
> in mind, that a join logical file does not allow keys
> from more than one 
> file, even though I suspect every new release of OS/400
> has formed yet 
> another DCR requesting this feature.  This might be
> possible with an index 
> on a view in SQL but I don't think that's allowed either.
>  I know you can 
> get the data this way in a normalized database via SQL
> but it's going to 
> do some work under the covers and performance may suffer.
> 
> Rob Berendt
> -- 
> Group Dekko Services, LLC
> Dept 01.073
> PO Box 2000
> Dock 108
> 6928N 400E
> Kendallville, IN 46755
> http://www.dekko.com
> 
> 
> 
> 
> 
> "Bill Meecham" <bmeecham@xxxxxxxxxxxxxxxxxxxx> 
> Sent by: midrange-l-bounces@xxxxxxxxxxxx
> 05/03/2005 01:33 PM
> Please respond to
> Midrange Systems Technical Discussion
> <midrange-l@xxxxxxxxxxxx>
> 
> 
> To
> "Midrange Systems Technical Discussion"
> <midrange-l@xxxxxxxxxxxx>
> cc
> 
> Subject
> Re: Left AS/400 and Returned
> 
> 
> 
> 
> 
> 
> That's not necessarily true since multi-format and join
> logical files can 
> be created and created much easier when the database is
> normalized.  The 
> reason shops don't normalize is more likely because it's
> difficult to 
> master and there is little perceived benefit.  Borrowing
> from another 
> thread, that's a large part of what case tools help
> with....normalization 
> and 'virtualization' of fields. 
>   ----- Original Message ----- 
>   From: michael@xxxxxxxxxxxxxxxxxx 
>   To: Midrange Systems Technical Discussion 
>   Sent: Tuesday, May 03, 2005 2:25 PM
>   Subject: RE: Left AS/400 and Returned
> 
> 
>   The reason that most vendors and shops don't have
> normalized databases
>   is because most vendors and shops don't use the data
> store on the
>   iSeries as a database - it's used as a system of
> indexed files.
>   Normalization in that scenario can hurt performance,
> because the
>   program would need to chain to several files to gather
> the information
>   needed to present to the user. There's no doubt that
> normalization is a
>   good thing for a database (at least 3NF), but
> normalization for indexed
>   files isn't as important or desired.
> 
> -- 
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Bradley V. Stone
BVS.Tools
www.bvstools.com