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

["Alan H Addison" <ahaddison@xxxxxxxx>]

One thing that has not been mentioned about the scenario mentioned below is
that the primary program must open the files in full access mode (update
add) if any maintenance is to be done to the files by program lower in the
invocation stack.


----- Original Message -----
From: "Buck Calabro" <buck.calabro@aptissoftware.com>
To: <rpg400-l@midrange.com>
Sent: Thursday, December 21, 2000 9:33 AM
Subject: Re: Named Activation Groups (was: DoW (WAS DoU...))


> 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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