Re: Why you shouldn't be afraid to use VARCHAR in RPGLE...

Hi Javier, this usually happens when the varchar is in a Ds and is not
properly initialized.

HTH
--
Marco Facchinetti

Mr S.r.l.

Tel. 035 962885
Cel. 393 9620498

Skype: facchinettimarco


Il giorno ven 5 dic 2025 alle ore 01:55 Javier Sanchez <
[email protected]> ha scritto:

> Thanks Charles!  Good to consider it!
> I once had a strange issue with a varchar variable.  It was empty, and
> taking the %LEN() of it was throwing me an exception.  I was expecting me
> to return zero, but the exception was that the length was not valid.
>
> Did not have much time to find out why that was, so I had to quickly change
> it to a simple CHAR and use %LEN(%TRIM()) of it.  Issue solved.  Never knew
> and did not want to investigate further with that, but what I've been doing
> is that I first test the original var that will be the value of the
> assignment, and that one is a CHAR type.  Not a good practice at all, but
> yes, I started to be scared of that.
>
> Will listen to better practices with them.
>
> TIA
> JS
>
>
>
> El jue, 4 dic 2025 a las 18:43, Charles Wilt (<[email protected]>)
> escribió:
>
> > I think I've maybe mentioned this in replies over the years.  But as I
> > posted "Why you shouldn't be afraid to use VARCHAR in RPGLE" as a reply
> to
> > a post on the midrange list, I thought the subject would be worthwhile as
> > its own post here.
> >
> > Back in 2016, a performance assessment by IBM's performance consulting
> team
> > reported back to my company that a certain (home grown) XML parsing
> routine
> > "was taking 23% of all cpu used by interactive jobs."  The PEX report IBM
> > collected even showed that that CPU was mostly being used on only 13
> lines
> > of code in that routine.
> >
> > I happened to see the report, and took a look at the routine in question.
> > What I saw was a bunch of the following:
> >
> > select;
> >   when %trim($level(x)) = 'something';
> >     ....
> >   when $trim($level(x)) = 'something-else');
> >     ....
> > endsl;
> >
> >
> > Obviously, doing the same work over and over again is a waste.
> >
> > So I simply changed level and a couple other related variables from CHAR
> to
> > VARCHAR. Ironically, I didn't need to use %trim() at all, since level was
> > originally loaded via:
> >
> > $level(x) = %subst(chars:1:stringlen);
> >
> > The next year's performance report noted that CPU consumption by our XML
> > parsing routine had dropped to less than 1% of Interactive CPU usage. The
> > sample size was somewhat small, so IBM also looked at the routine
> > explicitly and noted that CPU usage per call to the routine dropped by a
> > factor of 15. Additionally, my testing showed that response time per call
> > dropped from an average of 0.39s to 0.13s!
> >
> > Not bad for a day's work....
> > Most of which was regression testing!
> >
> > Now at the time, we had 7 or 8 big P50-tier POWER8 servers...each with
> > approximately 10,000 users. So, as you can imagine, interactive CPU usage
> > was and still is hugely important to us.
> >
> > Morals of the story:
> > - don't be afraid of VARCHAR
> > - lots of %trim() is often a red flag
> >
> > HTH,
> > Charles
> >
> > PS. Strongly consider VARCHAR for new DB fields. Just make sure you
> > ALLOCATE them appropriately.
> > --
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