From the user manual (DNP3 - Ignition User Manual 8.1 - Ignition Documentation), it states:
Buffered events can be enabled by setting the Queue Size property on the corresponding Tag Group to a number greater than 1. (See Queue Size on the Tag Groups page.) The number represents the number of buffer events that will be handled by the driver. The queue always keeps the most recent events, dropping older events. For example, if Queue Size were set to 20, and 30 value changes occur on the device while disconnected, then the 10 oldest events would be ignored by the driver.
After recovering from a disconnect, the driver will playback missed events from the driver, and update the value on the corresponding Ignition Tags by cycling through each event quickly, from oldest event in the buffer to the most recent. This value change will trigger value changes in certain systems. Specifically:
- alarms events (recent evens as well as alarm journal records)
- Tag History records (when the History Sample Mode is set to "On Change")
- Tag Events Scripts
Once finished cycling through the buffered values, the Tag will resume showing the live value.
Exactly how fast will the old values be cycled through? (can this be added into the user manual? @Paul.Scott )