Re: RPG III (RPG/400)

Dan,

CVTRPGSRC output is not 100% compatible, but is maybe 99% compatible.

The biggest issue is when the program uses the 'FREE' opcode, which does not exist in RPG IV (and, imho, never worked the way people thought it did, anyway, so most applications using it don't quite work right to begin with.)

However, a WHOLE LOT of effort went into making RPG IV extremely backward compatible with RPG III when it was released in V3R1. So CVTRPGSRC is really close... like I said, 99% compatible... I don't really think extensive testing is needed. But, you shouldn't just assume everything will work perfectly 100% of the time, either. I've found CVTRPGSRC to be a completely painless way to convert over, however.

(Compare that with converting RPG II to RPG III, for example -- that was much more painful! Even if you stayed with all program-described files, etc, the incompatibilities were much bigger between RPG II and RPG III!)

Now, if you do more than CVTRPGSRC does, such as using ILE concepts, converting to free-format, etc... that will definitely create more compatibility problems! (Which seems to be what most responders here on this e-mail group are referring to, and I can't see why since you never said you were doing that...)

-SK


On 11/2/2015 1:56 PM, Dan wrote:

It's interesting that I found this thread. Several weeks ago I was
searching on CVTRPGSRC to see what impact / issues one could expect to see
by converting RPG-III to RPG-IV.

We're using an old ERP package written in RPG-III. I have always been of
the mindset to convert any RPG-III source to RPG-IV before I modify it.
Especially now with RDi, where the outline view doesn't work with RPG-III
and hoop-jumping necessary to debug OPM programs. Unfortunately, I'm new
here and I'm getting pushback when I need to modify an RPG-III program.
The "standard" here is to convert only when it's a major rewrite or
something that needs to be done can't be done in RPG-III. The argument is
that any such application must be completely retested, so, while the effort
to convert is minimal, the big cost is in the effort to QA the app.

It's been at least 15 years since I did any significant conversions to
RPG-IV, but I never recall anything that "broke" as a result of simply
converting an app. NOTE that this means no attempts to convert stuff like:
MMDDYY MULT 10000.01 YYMMDD
to
Eval YYMMDD = MMDDYY * 10000.01
as an example. For the purpose of this discussion, I am strictly talking
about taking an RPG-III source, running CVTRPGSRC on it, checking the
conversion report, and compiling the RPG-IV program. The result should be
a functionally-identical program, 100% of the time. True? False?

When I was searching a few weeks ago to refute the idea that a converted
program needed to be *completely* retested, I found a few threads on the
RPG list from 2006 where some were asking about any “gotchas” with using
CVTRPGSRC. Comments from people whose judgment I trust on this list were
unanimous in that a converted app *must* be completely retested. If this
is still the case, I will have tremendous difficulty selling the idea of
converting every RPG-III program to RPG-IV anytime we do any kind of
modification, because the QA resources are extremely tight in this shop.
It seems to me that, with ~20 years of experience with CVTRPGSRC, surely
IBM would have worked out any kinks in the conversion and/or the report
identifying potential issues.

So, my question to the group is this: Has anyone *ever* found any
functional differences or issues after doing a straight CVTRPGSRC and
getting a clean report from the conversion report?

- Dan

On Fri, Oct 23, 2015 at 2:26 AM, Scott Klement <wdsci-l@xxxxxxxxxxxxxxxx>
wrote:

Vern,

To add to what Jon said, I will point out something that you probably
already knew, but maybe you (or others here) hadn't thought about...

RPG/400 was originally released in 1988. It was supplanted by the ILE RPG
(RPG IV) compiler in 1994. (and at that time, CVTRPGSRC was available to
make a painless conversion to RPG IV). that means:

RPG/400 was "the RPG to use" for 6 years.
RPG IV has been "the RPG to use" for 21 years since then.

The fact that a software vendor, who charges for their software and
maintenance, hasn't managed to update in 21 years is more than a little
absurd.

It requires only the tiniest investment to convert, and a company you are
paying maintenance to hasn't been able to do so in 21 years? 3.5 times as
long as the total lifecycle of the language they're converting from?
Yeah. Something is really wrong here.