I'm not going to get sucked into an argument over the virtues of block mode
vs. serial; both have their uses (yes, still!). But I do disagree about
performance of block mode vs. serial. Else telnet would have long ago been
replaced by some blocking solution!

That's it for me for this topic. Thanks for the enlightenment on
non-destructive screen update.

Dennis Lovelady
"Experience is the name everyone gives to their mistakes."
-- Oscar Wilde

No, it's just bending the rules of the block-mode UI concept that drove
business throughout the 70s, 80s and even the 90s, and still survives
today. Block mode is very efficient - it allowed remote processing on
1200-baud modem lines; there aren't many web application architectures
that could do that today. 5250 isn't particularly good for high-
bandwidth glitz but it works just fine for presenting textual data to
end users and getting their responses.


Ha! Thanks, Joe. Pretty slick. I hadn't thought to do this with
multiple formats.

Still feels like using a hammer to drive screws into the wall, though.

Dennis Lovelady
Reality is for those who can't face Science Fiction.

Dennis, here's the IBM book on the issue. Not terribly helpful but
it gives you the basic idea.

c= /com.ibm.etools.iseries.langref2.doc/dspfdq.html

The idea is that if the entry on the data queue is *DSPF, then READ
the display file, otherwise do whatever the entry says (which in
business case would be to upadte the data and WRITE the display


Great to hear it's possible, Jack. Care to elaborate on _how_ one
would post updates to the 5250 screen (barring status messages,
which are too limited to satisfy the need) without flicker, flash,
or disruption to user input? That is a challenge for which I have
never seen a solution with the
(naturally-blocking) 5250 display.

Dennis Lovelady
"Never lend books, for no one ever returns them. The only books I
have in my library are those that other folks have lent me."
-- Anatole France

Not only possible with RPG and 5250- it's been possible since
enabled display files to post status changes to data queues. FWIW,
I believe that feature was introduced on the System 38 from the
research I did supporting an such an application 12 years ago.
app was at least 10 years old at that time.

Was an undocumented maintenance nightmare until I used object
auditing to trace through the event chains, but I came to
appreciate it as one of the most elegant designs I've seen
implemented on the

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