RE: Service program signatures, and how to avoid unnecessarily recompiling programs that call service programs

What was the service program?
What PTF?

Paul

-----Original Message-----
From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of j.beckeringh@xxxxxxxxxxxxxxxxxxxxxxxxxx
Sent: Thursday, September 14, 2017 4:30 AM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: Re: Service program signatures, and how to avoid unnecessarily recompiling programs that call service programs

There is a subtle difference between a constant signature and the *CURRENT/*PREV method:

Say you have a service program, version 1, with 3 exports. You create version 2 by adding a new procedure, so there are now 4 exports. You have a program that uses the new procedure.

Now, if you run the program in an environment that only has version 1 of the service program present:
- If you used *CURRENT/*PREV you would get a signature error, because the service program does not have the new signature
- If you used a constant signature you would get an 'export not found'
error
Both are rather nasty, hard errors, so it is choosing between a rock and a hard place, but there is a difference.

BTW: Found this out when I moved a program to a different system and got the 'export not found' error on an IBM service program. On the source system a PTF had added a procedure to a service program; on the target system that PTF had not been applied. IBM had not used the *CURRENT/*PREV method for that service program.

Joep Beckeringh
Systeemontwerper
Pantheon Automatisering B.V.
Heerenveen

"Mark Murphy/STAR BASE Consulting Inc." <mmurphy@xxxxxxxxxxxxxxx>

14-09-2017 01:56

Re: Service program signatures, and how to avoid unnecessarily
recompiling programs that call service programs

Whether you use a constant signature, or use the *CURRENT/*PREV
method, you can only add new procedures to the end of the current
binder source group. You cannot reorder procedures in either case.
This is because only one version of the service program procedures are
maintained, and they are bound by relative location in the service
program. So if procedureC is in position 3 of the binder source when
it is initially created, it must be in position3 in every export group
in the binder source, and the groups that do not have procedureC must
not have 3 or more procedures defined. This is why the *CURRENT/*PREV
method of writing binder source is mostly busy work. It gives you
nothing, takes more work, and the rules for changing and recompiling
procedures stay the same.

Mark Murphy
Atlas Data Systems
mmurphy@xxxxxxxxxxxxxxx

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