RE: Normalization was Left AS/400 and Returned

[michael@xxxxxxxxxxxxxxxxxx]

Of course, a lot of RPG programmers don't use join logicals. Instead,
they provide their own indexed file navigation by getting a value from
one file, using that value to chain to another file, getting value from
that file, chaining to another file...and on and on. There's a divide in
AS/400-land...those that can/will use SQL or join logicals and want a
normalized database, and those who have a series of indexed files and
do their own navigation. Basically, if a programmer wants to use more
modern techniques, the iSeries can support them. And of course, if a
programmer still wants to code in RPG/II, they can. The ability to use
30 year old techniques is a 'feature' on the iSeries.


> -------- Original Message --------
> Subject: Re:  Normalization was Left AS/400 and Returned
> From: rob@xxxxxxxxx
> Date: Tue, May 03, 2005 2:55 pm
> To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
> 
> 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>
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> 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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