Re: Size of Service Program

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

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.