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.

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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 ?

Simon Coulter wrote:

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.

I think that David might have the right idea, but not asking quite the right question. To simplify David's case, lets suppose we have PGM0, consisting of modules MOD_0 and MOD_UTIL. We also have PGM1, consisting of MOD_1 and MOD_UTIL.

If I now run PGM0 which calls PGM1, wouldn't there essentially be two copies of the code for MOD_UTIL in memory? I think this must be the case, since if I change MOD_UTIL and rebind PGM0 but don't rebind PGM1, PGM1 will still use the "old" version of the MOD_UTIL code.

In any case David, I would echo Simon's recommendation to start using Service Programs. It's really not hard, and it beats the "compile the world" maintenance model hands down.