I re-read Chandra's original post, and I did not see anywhere that the process in question was for the purposes of looping through a set of records. It may have been; I just didn't interpret it that way. My interpretation was "How to determine if a specific record is in the table." Such as a customer number in the customer master; not finding the records for a specific customer in, say, a history file.
Personally, I'm a big fan of standards, though my own (it's a one-man shop!) change over time. Either because (a) what was true yesterday is not true today (usually meaning, "I was wrong"), or (b) I found a better way (or a method that I like better). A good example of (b) would be subprocedures -vs- subroutines. I was a Johnny-come-lately to subprocedures but, while I still use subroutines (usually for control mechanisms), more and more I use subprocedures so my standards changed.
If the reason for the diktat is for performance issues, Chandra (or the Sr. Programmer) would need to devise a test that could measure the case(s) for which their rule applies. For example, in a batch program against a ton of records (how many bytes in a ton?) it may be that SETLL/READE is more efficient than CHAIN and, if so, might significantly reduce the job's run-time. But for an interactive program where one is going for a specific record (customer master example), what's a couple of nanoseconds among friends?
My personal preference for record access is to use CHAIN when going for a discrete record, and SETLL/READ when going for (potentially) a group of like records (as illustrated by Jeff and others). For me replacing CHAIN processing (discrete record access) with the SETLL/READE method would be confusing, but only because that is the way that I was raised. The opposite might apply in Chandra's shop.
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 jdavis@xxxxxxxx
Sent: Tuesday, September 02, 2008 9:37 AM
To: RPG programming on the AS400 / iSeries
Subject: Re: Chain vs SetLL/ReadE
My quess for the following code
SetLL (KeyFields) FIleName;
ReadE (KeyFields FIleName;
DoW Not %EOF(FIleName);
do my stuff
ReadE (KeyFields) FileName;
EndDo;
Would be for the following, the chian function will not return a %EOF
condition, it returns a %Found. So using a chain will add an extra check
in your loop.
Chain (KeyFields) FIleName;
If %Found(FileName)
DoU Not %EOF(FIleName);
do my stuff
ReadE (KeyFields) FileName;
EndDo;
EndIf;
Thanks,
Jeff Davis
Dental Network of America
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