This may seem evident, but trying to figure out a way to log datapoints ONLY while an external process is running - perhaps by triggering an event in some watchdog point - or by scripting of some sort. Idea is, a process runs for, say, 3 hours per day; for a variety of reasons (charting being one of them), several points are logged at second or even sub-second intervals but don't want them logged when the external process is idle. Communication is via modbus, primarily TCP.
Perhaps its possible to prevent (or enable, for that matter) modbus reads depending on a datapoint state.
Any thoughts appreciated!