I don't use join logical too often, simply because the need isn't usually there. However, in the few cases when I have it has been to make the programming easier. That is, I don't have to even think about opening multiple files and doing any number of steps in the code to accomplish what I want to do. The logic is usually straight line, short, and more easily comprehensible than it would have been with multiple files.
Jerry C. Adams
IBM System i Programmer/Analyst
B&W Wholesale
office: 615-995-7024
email: jerry@xxxxxxxxxxxxxxx
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Thursday, September 18, 2008 9:48 AM
To: RPG programming on the AS400 / iSeries
Subject: RE: Joins vs. explicitly reading multiple files
<sarcasm>
Not only that, but joins (and views) make Query/400 too easy for the users
to understand, and, if you have developers that can only handle using RPG
in the basest definition (Report Program Generator) then you might put the
slackers out of a job.
</sarcasm>
Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com
"Murphy, Mark" <MurphyM@xxxxxxxxxx>
Sent by: rpg400-l-bounces@xxxxxxxxxxxx
09/18/2008 10:41 AM
Please respond to
RPG programming on the AS400 / iSeries <rpg400-l@xxxxxxxxxxxx>
To
"RPG programming on the AS400 / iSeries" <rpg400-l@xxxxxxxxxxxx>
cc
Subject
RE: Joins vs. explicitly reading multiple files
You are going to have to test it to make a judgment. I don't use join
logicals unless there is a very
good reason to do so. I use scenario B, and we have good performance. It
is possible that we could
get better performance with scenario A, but I don't have to deal with the
complexities of promoting
join logicals to production, and impact analysis is simplified as well. In
addition, joins can
perform poorly depending on the specifics of the files being joined.
My suggestion would be to pick a way for your shop standard based on you
shops needs, and use that
method unless you can't. Only optimize when performance is poor enough
that the cost to optimize is
easily recovered in much better performance. I would suggest that the
difference between scenarios A
and B is nanoseconds in most cases.
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of James Lampert
Sent: Wednesday, September 17, 2008 1:16 PM
To: RPG programming on the AS400 / iSeries
Subject: Joins vs. explicitly reading multiple files
Consider 2 scenarios (both using native Record Level Access):
Scenario A: We read from a join-logical with 5 different based-on
physicals
Scenario B: We read from the 5 based-on physicals individually, either
directly or using simple logicals.
In terms of performance, is there any reason to prefer one over the other?
--
James H. H. Lampert
Touchtone Corporation
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