Re: ILE RPG CGI and Activation Groups

hi Mike,

I have been reading up on activation groups and how they relate to
CGI apps. I understand the concept but I have a design issue that I
can't see having been discussed as yet.

For me, I tend to think of my programs (or *SRVPGMs) in two different categories:

a) Initial programs (Called directly from the command-line, menus, CGI, etc)

b) Sub-programs or service programs. These are never called directly from a menu or command-line, but are called by other programs.

Note that whether you're using CALL, CALLP or CALLB really doesn't matter. They all work the same way... Initial programs should either use a NAMED or *NEW activation group. Sub-programs should always (well, almost always) use *CALLER.

The next question is really how do you want things to behave? If you want programs to ALWAYS leave their resources open, including files, variables, etc. Then you should use a NAMED activation group for the initial programs. This way, they'll remain loaded into memory. If you leave *INLR=*OFF, they'll also leave their files open, etc. This has the best performance, since most startup tasks only need to be done once.

On the other hand, if you want all of the resources to be automatically cleaned up when the initial program ends (including all resources used by all sub-programs) then use ACTGRP(*NEW), and (no matter if LR is on or off) it'll close all files, free up all memory, and unload all programs from memory (including the sub-programs).

Because of all of the extra work involved in opening & closing files, loading/unloading programs from memory, etc, ACTGRP(*NEW) doesn't perform as well. The performance difference doesn't matter if the program is only called once or twice. But if it's called many times, the performance will become significant.

Since most CGI programs require many, many calls to get the job done, most CGI programs lend themselves to using a named activation group. If you need to close the files, etc, when you perform a backup (or something like that) you can always end the HTTP server before your backup, and then restart it afterwards. That way, you only incur the performance penalty once...

Hope that helps.