I have an OPC DA interface running and over the last month or so it has started to exhibit some strange behaviour. The number of scans skipped starts to increase and then it max's out. The heartbeat starts increasing in time scale from 1 second updates to over a minute. The interface then stops collecting data, but the heartbeat continues to work. I can't see anything in the event logs of the server or anything within the PI logs for the interface.
What causes scans to be skipped? Could it be down to the server not running particularly quickly? I've just run pigetmsg and it prints out the lines like an old dot matrix printer, character by character rather than line by line. When we do a reset of the interface software it clears the problem for a while but then comes back after 5-6 days.
The trend bellows shows the change in skipped scans and the corresponding drop in scan counts. I've removed the heartbeat trace as it would block everything else out. The substitution arrows are for the scan count tag mostly, and a couple from the scan skipped tag
Anyone got any ideas as to what might be causing this? I have 3 other OPC interfaces and they are working fine. Below is a screenshot of the results returned from running pigetmsg. The previous summary had scan on time %'s > 97.5% for all classes. In the screenshot below the scans on time are much lower. I'm checking scan class 1 to see if I have any rogue tags configured which may be causing the issue but most of the tags in this group are digital tags so wouldn't be changing at 1 second intervals. Is there anyway to see what tags are sending the most data??
All help greatly appreciated