Seen a solution for a similar issue ( displaying current stock prices as
they change ). Display files can be configured to write entries to data
queues upon user action (press enter key or command key). Been available
since the System 38 (except for the database trigger).

So the display program is a loop waiting on arriving data queue entries,
whether from the database or user keyboard events.

To be notified of on-hand quantity changes, your display program would need
to register its interest in such events for items it is currently
displaying- a table with a row for each item, a data queue to notify, and
maybe a reference to the job and current level being displayed.

Then add an after trigger on your inventory table which will check the
current notification registry for entries for the item number just updated,
and generate a data queue entry for each registered listener for the
updated quantity.



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