Hi,
We have not yet implemented the use of service programs. So each program has its own copy of the code.
When a procedure is modified, we recompile all programs that reference a procedure in the module of the procedure that is modified. This is making installation longer each time, as the modules become bound to more and more programs and more programs must be recompiled.
If we have 50 people using the same interactive program that weighs 40 Mb, made up of many modules bound by copy and no service programs, are there 50 copies of that program in activated or is it shared ? Can we imagine any performance differences with the use of service programs instead of modules?
Thanks.
-----Message d'origine-----
De : rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de Mark S. Waterbury
Envoyé : mercredi 30 juillet 2008 22:40
À : RPG programming on the AS400 / iSeries
Objet : Re: Question about service programs
Hello, Charles:
The executable code within *PGMs and *SRVPGMs is "reentrant" so the executable code is "shared" (read-only pages) across multiple jobs (and so is a lot of other stuff in the vast single-level-storage address space).
Unique to each job is the "activation" of each program and service program, which includes the allocation of static and automatic (dynamic)
storage for the programs, etc. The "activation group" is the container
for all of these various 'activations' of *PGMs and *SRVPGMs, allowing for programs to control "clean-up" by activation group. You can think of each job as initially having just one activation group. (Actually, there are always at least two AGs, the DAG or default activation group where OPM programs must run, and an ILE activation group where ILE *PGMs
run.) There is also a "System-wide Activation Group" (or SAG) where many ILE components of OS/400 run, so they are initialized once (usually at IPL) and they can remain activated and "in use" across the entire system.
As others have pointed out, one way you can do something similar is to create a (never-ending) "server job" to service requests.
Traditionally, (going back to System/38 CPF), you would implement this approach using data queues. Today, you might also want to consider using a TCP/IP sockets interface. One advantage of the TCP/IP sockets approach is that the client programs can run on a PC under Windows or Linux, or on another Unix or Linux server, or even another iSeries system, while the "server jobs" run on your System i. There are various approaches for spawning multiple jobs (or threads) so that as the frequency of requests (or volume of transactions) increases, your server can "keep up" or "scale up" as needed. (In fact, this is exactly what most HTTP servers do.)
I hope this explanation helps?
All the best,
Mark S. Waterbury
Charles St-Laurent wrote:
Hi!
I wonder if what I want to do is possible on iSeries (V5R4).
I want to load many service programs in a kind of shared memory and
then use the loaded service programs from interactive or batch jobs,
so the loaded programs won't be loaded each time I start a new batch
or interactive job that wants to use them.
For example:
1) I load all my service programs once and initialize them correctly
2a) I submit a job and I want the submitted job to use the loaded
service programs that have been loaded previously and passing them
parameters
2b) I launch an interactive job and I want this interactive job to use
service programs that have been loaded previously and passing them
parameters
I read about activation groups. Activation groups are effective within
the same job. But in my case, I also want to use persistent programs
between jobs (each batch job is a new job and I don't want my service
programs to be allocated/released each time). I want my batch jobs to
execute previously loaded service programs, each time with different parameter values.
Charles St-Laurent
Consultant Berco
Technologies
Industrielle Alliance, Assurance auto et habitation Téléphone : 418
650-4600, poste 3216 Sans frais : 1 800 463-4382 Télécopieur : 418
650-4612 Sans frais : 1 877 650-4612 Courriel :
charles.st-laurent@xxxxxxx <mailto:pcharles.st-laurent@xxxxxxx>
www.inalco.com/assurancegenerale
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