Re: Size of Service Program

On 11/8/2010 12:28 PM, DeLong, Eric wrote:

As always, when a service program module gets activated, storage must
get allocated and initialized, which is costly.

Some storage, yes... but not all storage is allocated when a service program is activated.

The whole idea of activation groups is to all ONE startup cost
(activation), with reuse of the already activated code as needed.

I don't agree with that assessment at all. Activation groups have several purposes, but "loading everything at once" is not one of them. They do provide a way to _keep_ things activated so you don't have to pay the activation cost multiple times... but I don't think they expect you to activate everything at once in "one startup cost."

If you do something silly, like making your service program module
start ACTGRP(*NEW), your huge service program could be a performance
nightmare.

The CRTSRVPGM command doesn't offer the option of ACTGRP(*NEW).

Where, I'm a little fuzzy is whether all modules in a particular service
program are activated at the same time. We only use single-module
service programs here, so I haven't had to deal with this yet.

Activation is done by the *PGM/*SRVPGM. Modules are just building blocks of *PGM or *SRVPGM objects and are not used at run-time.

However, the files that are global to a given module are opened the first time a procedure from that module is *called*, therefore the first time you call any procedure in a module, there's an extra startup cost. That might be what you're thinking of? Technically the modules aren't used at that point, but there are still resources scoped to the routines that came from a particular module.