Re: Question about service programs

On 31/07/2008, at 6:10 PM, David FOXWELL wrote:

We have not yet implemented the use of service programs. So each program has its own copy of the code.

Then you should start using service programs. It's not difficult.

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.

Yuck! Maintenance nightmare. Exactly what service programs are designed to avoid.

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 ?

All programs on OS/400 are re-entrant. There is only one copy of the code loaded. Each user has their own copy of variable storage but they all share the same copy of the code--even if they are running in different main storage pools. It's been that way since System/38.

Can we imagine any performance differences with the use of service programs instead of modules?

No. Only problem I am aware of is that HUGE service programs take some time to activate so it's possible to see increased start-up times for program activation but I believe some work has been done on recent releases to mitigate this. (And by HUGE I mean REALLY HUGE--it is unlikely that most people will ever experience this unless they shove all their procedures in a single service program and that's as stupid as binding common procedures into every program.)

Regards,
Simon Coulter.
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