RE: Optimizing File I-O in RPG IV/ I-Series

Simple example: You can create a case insensitive index. If you do a SETLL 
with 'FLEMING', you might get a record with a key of 'Fleming'. READE will 
handle it for you, a simple compare won't.

Joep Beckeringh






"Fleming, Greg \(ED\)" <GFLEMING@xxxxxxxxxxxxxxxxxxxx>
Sent by: rpg400-l-bounces@xxxxxxxxxxxx
23-11-2005 15:07
Please respond to RPG programming on the AS400 / iSeries
 
        To:     "RPG programming on the AS400 / iSeries" 
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        Subject:        RE: Optimizing File I-O in RPG IV/ I-Series


I don't quite understand what her advice is. 

What does she mean by "Using READ and checking the key yourself from the
INFDS" ?  I'm not talking about using the INFDS, I'm just talking about
putting in some logic like:

If FileField <> KeyField
   Leave
EndIf

I can't see how that can cause any danger or be "less accurate" than
READE in any way.  The only danger comes if the programmer fails to do
his comparisons correctly, or forgets to check for %EOF. 

I like the way READE looks in the code better, too.  And I was kind of
disappointed when we stopped using it, until I saw how much faster our
programs were running.   Granted, speed isn't an issue on every program,
but I think that the bigger the file you're reading, the worse of a dog
READE can be. 

An example of the kind of thing we saw tremendous improvement is where
we're reading through a couple million customers, and setting LL for
each one of those on a 55 million record purchase history file.  I don't
recall the exact difference in run-time, but it wasn't just shaving a
few seconds, it was a couple hours. 

Anyhow, as the original poster (Jim, I believe) was having a performance
issue, I think he would do well to try getting rid of his READE and see
if it doesn't help.  I'll be surprised if it doesn't. 

>-----Original Message-----
>From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]
>On Behalf Of RPower@xxxxxxxxxx
>Sent: Wednesday, November 23, 2005 8:28 AM
>To: RPG programming on the AS400 / iSeries
>Subject: RE: Optimizing File I-O in RPG IV/ I-Series
>
>Well,
>I think I'll be taking Barbara's advice on this.  I do so love reade.
>
>Ron Power
>Programmer
>Information Services
>City Of St. John's, NL
>P.O. Box 908
>St. John's, NL
>A1C 5M2
>709-576-8132
>rpower@xxxxxxxxxx
>http://www.stjohns.ca/
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