RE: Should I replace all CHAIN, SETLL, and READs to SQL -- RPG400-L

Charles,

Thanks for the information

John

-----Original Message-----
From: Charles Wilt [mailto:charles.wilt@xxxxxxxxx]
Sent: Friday, November 02, 2012 12:32 PM
To: RPG programming on the IBM i / System i
Subject: Re: Should I replace all CHAIN, SETLL, and READs to
SQL

Yes, SQL allows access via RRN, but you do not want to use
it. As accessing via RRN forces a full table scan.

Unless you plan to add a unique key, I'd stick with RLA.

Furthermore, simply replacing RLA op-codes with the SQL
equivalent is usually a bad idea; since the program is still
designed for record at a time processing. RPG RLA is
optimized for record at a time, SQL is not.
SQL is designed to process sets. May not be such a big
deal in an interactive program...but for a batch program
you'll end up with horrible performance.

HTH,
Charles

On Fri, Nov 2, 2012 at 11:06 AM, John Allen
<jallen@xxxxxxxxxxx> wrote:

I have been thinking about changing all CHAINs SETLLs and

READs in our

software to SQL

Our programs use these operations for various reasons such
as:

Simple SETLL to check if a value is valid

Reading records for loading subfiles

Chaining by RRN (used in subfile processing, the input

file does not

have a unique key so RRN is stored in Subfile then used

for accessing

the original record)

Reading and chaining to several files for processing

thousands of

records and doing validations, calculations etc.

My main concern would be:

How this would affect performance

Does SQL allow for accessing records by RRN.

Does anyone have any thoughts on why this is a good or bad

idea

Thanks

John

--
This is the RPG programming on the IBM i / System i

(RPG400-L) mailing list

To post a message email: RPG400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the