RE: Separation of Presentation, BL, and I/O Tiers

Interesting questions.  How does the Mediator address these issues, David?

> -----Original Message-----
> From: Joe Pluta [SMTP:joepluta@PlutaBrothers.com]
> Sent: Thursday, April 11, 2002 3:08 PM
> To:   rpg400-l@midrange.com
> Subject:      RE: Separation of Presentation, BL, and I/O Tiers
>
> > From: Jon Paris
> >
> > Having said all that - given that the routine you call is a
> > generic one used
> > by many different functions, I'm not convinced that dynamic
> > memory is really
> > needed.  Why not just use fixed memory in the callee and map to that.
> Or
> > for that matter use IMPORT/EXPORT.
>
> Whee!  Now you guys are getting into the FUN stuff!
>
> I need to retrieve dynamic amounts of data, data whose size cannot be
> determined at compile time.  Do I allocate the maximum amount of storage,
> or
> dynamically allocate the storage as needed?  Well, that depends on a whole
> bunch of things.
>
> Let's look at static allocation in the callee.  First off, how many of
> these
> modules are you going to have?  If you're talking about creating a nice
> 16MB
> buffer for every file, and you have 100 files, you're talking about 1.6GB
> of
> storage.  For every job.  That's a pretty serious amount of storage.
>
> And what happens when you need to do this recursively?  Let's say you use
> this procedure to handle a bill of materials.  You call the subprogram to
> get the parent's components.  You start processing those records, and the
> first thing you do is go get the components for the first child.  Well,
> since everybody is sharing the same memory (in the callee), then this call
> is going to wipe out the parent's component list.  Life becomes totally
> rancid, dude.
>
> On the other hand, how do you manage dynamic memory?  Do I have a big fat
> buffer that I read everything into, and then allocate a buffer of the
> correct size when I'm done?  Big waste of memory.  Or, I can allocate a
> smaller chunk at a time (say 100 records), and then extend the chunk every
> time I need to.  But this involves copying the old records every time I
> extend the space.  Thirdly, I could allocate space a chunk at a time, and
> then paste them all together at the end.  A nice compromise, but not
> particularly intuitive at first glance.
>
> On top of all this, the caller has to remember to release the data.
> Whether
> the caller does the release or calls the subprogram to do the release,
> this
> is still under the control of the caller.
>
> Whoo hoo!
>
> We're having fun now!
>
> Joe
>
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