Re: CHAIN vs SETLL/READE -- RPG400-L

The intent here is to fetch the data record.

Actually there are 2 separate conditions: For one file, the record would
mostly be found, for other it would mostly not be found (I still need the
data whenever it is found).

Would the recommendation be different in these 2 cases?

Vinay

On Tue, Oct 15, 2013 at 8:13 AM, Briggs, Trevor (TBriggs2) <
TBriggs2@xxxxxxxxxxx> wrote:

Eric,

Would a "Not found" condition on a CHAIN cause a MONITOR to execute the
ON-ERROR logic?

Trevor Briggs
Analyst/Programmer
Lincare, Inc.
(727) 431-1246
TBriggs2@xxxxxxxxxxx
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of DeLong, Eric
Sent: Monday, October 14, 2013 5:57 PM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: RE: CHAIN vs SETLL/READE

If the intent is to page data into storage, and to note when exceptions
occur (Chain failure - Not Found), then Chain HAS to be faster overall
than SETLL, then an IF to determine existence status, then another I/O
to page data in...

Traditional usage of CHAIN still requires an IF expression to test the
results of the operation. This logical test is minimal, but it must be
evaluated EVERY TIME the I/O is performed. Perhaps putting the CHAIN
into a Monitor block, then defining an on-error handler for the
exception might yield the best performance, since the exception status
does not need to be evaluated on each I/O iteration.

But, really, I'd code it to its simplest form, that most clearly
expresses my intent. Again, I think, CHAIN is the clear winner.

-Eric DeLong

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Briggs, Trevor
(TBriggs2)
Sent: Monday, October 14, 2013 12:47 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: RE: CHAIN vs SETLL/READE

My first reaction is that a CHAIN would be faster than a SETLL and READE
to retrieve a single random record. However, this is assuming that your
reads have to be random and what percentage of the records you'll be
reading from the file. If you are going to be reading the majority of
records from a multi-million record file, re-jigging your logic so that
you could read the file sequentially (if even you ignore some of the
records in your code) could be advantageous.

Trevor Briggs
Analyst/Programmer
Lincare, Inc.
(727) 431-1246
TBriggs2@xxxxxxxxxxx
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Vinay Gavankar
Sent: Monday, October 14, 2013 12:44 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: CHAIN vs SETLL/READE

Hi,

I know this has probably been hashed a lot of times, but which of this
is
more efficient?

Doing a direct Chain or a SETLL and if %EQUAL doing a READE

I am accessing on a full unique key, but performing this millions of
times
in a batch program.

Most of the times the record WILL be found.

Thanks
Vinay
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