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

["Fleming, Greg \(ED\)" <GFLEMING@xxxxxxxxxxxxxxxxxxxx>]

I suppose I should also emphasize that this does require that the file
or logical you are using is sorted in the same order as your key. 

So when I said READE is like Chain, what I mean is that is uses a key
and does a comparison against the whole file, whereas READ just moves
right on to the next record without reading through anything.  If your
file is already sorted in the order you want, then READ is definitely
faster than READE.



>-----Original Message-----
>From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]
>On Behalf Of Fleming, Greg (ED)
>Sent: Wednesday, November 23, 2005 8:05 AM
>To: RPG programming on the AS400 / iSeries
>Subject: RE: Optimizing File I-O in RPG IV/ I-Series
>
>I'm sure the gurus can explain it better than I, but READE actually
>performs a bit counter-intuitively.
>
>It actually resets the pointer every time it is invoked.  So you setLL
the
>first time, then when you READE it looks at your key and reads through
all
>the records again to get to the next one, and so on.  At least that's
the
>way it's been explained to me.  We made it a standard in our shop to
never
>use READE, and when we did, the performance of our programs improved
>dramatically.
>
>Instead, we use:
>
>Key SetLL File
>DoW 1 = 1
>Read File
>If %Eof or Key <> Record
>   Leave
>EndIf
>Process Record
>EndDo
>
>
>Greg
>