On 12/03/2008, at 7:32 PM, David FOXWELL wrote:
After much reading I think the benefits of using service program is
beginning to sink in although without practical experience I admit
having some difficulty. Currently, we only use modules bound by
copy into many different programs and we need to explore the
possiblities of converting to the use of service programs.
I thought I read somewhere that service programs do not run in the
*DFTACTGRP, but I can't seem to find that information again. Could
someone confirm if this is true or not?
It is both. You cannot compile a program that uses external
procedures and have DFTACTGRP(*YES). The compiler complains. However,
you can create a program with ACTGRP(*CALLER) and invoke that from a
program running in the default activation group. This will cause the
second program (and possibly any programs and service programs it
calls) to run in the default activation group.
Prompting the CRTSRVPGM command and examining the ACTGRP keyword
would show you that the only values are *CALLER or a name of your
choice. Compare this with the ACTGRP keyword on the CRTBNDRPG
command. You will notice that CRTBNDRPG also supports DFTACTGRP which
is absent from CRTSRVPGM. Thus your question has been partially
answered. However, The default, and usual, setting for a service
program is to run in its caller's activation group. If such a service
program is invoked from a program running in the *DFTACTGRP then the
service program will also run in the default activation group. This
is a bad state of affairs. Avoid it by either specifying a named
activation group on your service programs, or create your main
programs with a named or *NEW activation group and allow all service
programs to use *CALLER. I use both methods according to my needs.
What kind of problems could we expect to run into when mixing ILE
and OPM?
You cannot call service programs from OPM so either you mean ILE
running in *DFTACTGRP, or you will have to create wrapper program
objects to be invoked from OPM, or you will have to convert your OPM
programs to ILE.
You cannot unload service programs from the default activation group
except by ending the job (e.g., signing off). This makes development
and testing awkward.
ILE and OPM (and ILE running in *DFTACTGRP) have different scoping
for overrides, opens, and commitment control. ILE gives you more
granular control over these things which is a good thing but can take
some getting used to.
As I recall the ILE concepts manual gives some information about a
mixed environment. It's been ages since I read that manual so I
cannot be sure but it is a good read and explains ILE in great and
understandable detail.
Also, search the archives. You are not the first to ask these
questions in the 15 years or so that ILE has been available.
Regards,
Simon Coulter.
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