Re: LVLCHK(*NO) - Looking for a Techdoc on why this is a bad idea (x-posted to RPG & MIDRANGE)

Rob,

Even if each program had it's own logical, the access path overhead isn't a
big deal since any logicals with the same set of keys would share the same
access path. I suspect you'd end up with just a few actual access paths
even if you had lots of logicals.

Naming of that many logicals would be more of a concern for me.

You mention Infor doing it right with logicals for RLA (though not
SQL)...I'm curious, did Infor have a unique logical for every program? Or
do they just version the logicals? Exmample, ITMMSTLF01 is the base LF.
When a new field is added to the the physical, any program needing it would
be changed to access the newly created ITMMSTLF02.


Charles


On Tue, Dec 1, 2015 at 9:19 AM, <rob@xxxxxxxxx> wrote:

Your last paragraph is a huge thing. Granted, I'm not a big fan of each
program having their own logical as the access path overhead could get
huge but each logical that is created should explicitly select the columns
listed, even if it is all columns that are currently in the table.

Infor does this with their logical files and that makes adding columns to
the base tables easier. Not that everything they do is to be used as the
guiding example as they use no constraints of any kind and a bunch of
other stuff.

Infor did follow the SQL guide and when they used SQL instead of RLA they
do access the base tables. This wouldn't have been a bad thing but they
royally screwed up by doing a 'select * into :fileds' kind of logic. Never
do a select *. Now when you add new columns to the base table you have to
recompile all programs that do this.
And when you start thinking about adding columns with special
characteristics like 'implictly hidden' and what not, argh...


Rob Berendt
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From: Charles Wilt <charles.wilt@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
"RPG programming on the AS400 / iSeries" <rpg400-l@xxxxxxxxxxxx>
Date: 12/01/2015 09:09 AM
Subject: LVLCHK(*NO) - Looking for a Techdoc on why this is a bad
idea (x-posted to RPG & MIDRANGE)
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



All,

I'm looking for a bigger stick than my own knowledge to use to beat some
sense into a vendor with regards to the use of LVLCHK(*NO).

Is anybody aware of a authoritative document on the subject?

I'd assume such a document would also go into the alternative solution of
"logical file access only" whereby all native RLA I/O is done via logical
files with explicit formats.



Thanks!
Charles
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