Re: Named Activation Groups (was: DoW (WAS DoU...))

[Buck Calabro <buck.calabro@xxxxxxxxxxxxxxxxx>]

Patrick Conner wrote:

>This is a very nice example of how to organize activation 
>groups (AGs), but what is the real benefit? When I first 
>started ILE about eight months ago I never saw any real 
>advantage to them. In OPM the only time I ever used an
>open data path (ODP) is when I did an OpnQryF just 
>before calling a program and then deleted it before moving 
>on to the next program. 

I guess when you say "ODP" you mean Shared Open Data Path.  The key here is
Shared.  The primary benefit is performance.  If you call an RPG program it
does a bunch of work before it executes your first C spec.  Initialise
variables, set up file buffers, open files, etc.  If your application is
broken into a main program and several sub-programs, you can see a large
performance benefit by using shared file opens and not setting LR on in the
sub-program.  

ovrdbf share(*yes)
MAIN
  prepare all file buffers
  init vars
  open all files
  CALL SUB
    re-use file buffers
    init vars
    re-use open file
    do some work
    return (no LR)
  do some work in MAIN
  CALL SUB (again)
    re-use file buffers
    re-use variables
    re-use open files
    return

>AGs seem to add a lot of complexities to RPG programming. 
>I believe it is the primary block to getting programmers to 
>convert to ILE. I don't just mean RPG IV, but real ILE. 
>The ILE concept book makes a big deal out of ODPs, 
>but like I stated earlier. I hardly use them.

I like to use the word "flexibility" instead of "complexity" - it somehow
seems more positive!  Yes, AGs are one more thing to think about when
designing an application, but I truly believe that this is a Good Thing.
Far too many midrange programmers fail to think of the application as a
whole - they think only of "this one program" and not how it interacts with
all the others in the system.  This is a simple approach, but it makes
fragile applications because of subtle interactions that are by-products of
writing each individual program.

As for "I hardly use shared file opens" you aren't alone.  There aren't that
many midrange applications that take advantage of the technique even though
it has been available to us since the S/38 days.  I believe that one reason
for this paucity is the simple fact that few programmers hear about it.
Discussing it here will "light a candle" in somebody and spread the idea to
at least one new person.  That's progress!

Buck Calabro
Aptis; Albany, NY
"Nothing is so firmly believed as
 that which we least know" -- Michel Montaigne
Visit the Midrange archives at http://www.midrange.com
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