Re: Early Client Server on the AS/400 -- MIDRANGE-L

Nina:
You are correct in your assumptions.  DDM does use ICF as its communications
mechanism, however there is much more overhead involved in using DDM vs.
ICF.  DDM is simple, thus it was developed to handle all sorts of remote
data access options, thus there is lots of over head.  You specific ICF
program was written to only do one thing and do it well, aquire a device,
evoke a target program, read the record you want and return it to the
calling program.  Each subsequent read did not require the aquire, evoke and
security checking, thus your performance was much better.  Each has its own
merits, it 2 AS400s are on the same network at 100megabit and you open a
file via DDM, chances are you won't notice any performance degredation, on a
9.6 line you will.  However DDM does not read the entire file.  When you
have an RPG program that reads a local file with a CHAIN, it only reads one
record, the same is true with a CHAIN to a DDM file, only one record is
read, however there is also all the overhead associated with starting the
comm session to the target machine.  DDM is VERY handy for may applications.
Carl
Carl Galgano
EDI Consulting Services, Inc.
540 Powder Springs Street
Suite C19
Marietta, GA  30064
770-422-2995
mailto: cgalgano@ediconsulting.com
http://www.ediconsulting.com
EDI, Communications and AS400 Technical Consulting

-----Original Message-----
From: nina jones <ddi@datadesigninc.com>
To: MIDRANGE-L@midrange.com <MIDRANGE-L@midrange.com>
Date: Sunday, January 03, 1999 2:31 PM
Subject: Re: Early Client Server on the AS/400


>> DDM just does a chain to the remote system and only returns the data that
>> you requested over the comm line.  The whole file definitely does not
have
>> to be transfered.  This is done via an ICF file.  The source system
evokes a
>> program on the target system that retrives the record requested via the
>> CHAIN, and then only returns the record requested.  Note though that the
>> entire RECORD is returned, not just the field you need.
>
>i thought ddm and icf were two different things.
>
>when we tried ddm, we set up file overrides to the remote system.  and
response went down
>the drain.  in the override, how do you tell it to only send back a piece
of data.  i
>thought the whole idea was the file was accessed just like it was a local
system.
>
>we switched to the source/target programming method, where the source
program would
>aquire the correct system, send the request, the data was created on the
target system,
>and then received back via icf.
>
>nj
>
>

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