PCo 2.0 does not recover after "System is too busy" error.

Question

We run PCo 2.0.1.8 with multiple agents (OPC-DA 2.05a --> MII 12.1.6.Build(91)).
Sometimes our MII-Server is under heavy load and is not able to process PCo messages anymore. Therefore one PCo agent stops working and logs this message:
"System is too busy. Incomming message processing is halted until the system becomes less busy."
The other agents stop working as well. They never recover and start sending messages again.
It is not about retrying to a send old message again. We set "Maximum Retry Attempts" to 3 and "Retry Interval" to 1.
It is about sending new messages after OPC items changed. Our OPC servers change values at least once a minute, which should result in new messages.
Any suggestions to solve this issue?
Regards,
Martin

Answer 1

Kevin,
of course we try to avoid this error and investigate the reason, but it may happen and we would like PCo to recover from it.
PCo and its push technology is the right choice for us. We have to get informed when an OPC value changed. We do expression evaluation as well, but a few machines change their values so often that we get notifications every 3 to 5 seconds. And this is the reason for the very short retry interval of 1 second and 3 retry attempts in this case. If the notification comes too late, the information is outdated and we don't need it anymore.
The retry interval is not the point. When the MII server becomes less busy and is ready to process new notifications again, PCo does not even send new notifications. The agents have to be restarted to work again. That's our problem.
Expected behavior of PCo
00:00   OPC change --> MII idle --> Send Notification --> OK
00:03   OPC change --> MII busy --> retry 3 times, then throw away --> OK
00:06   OPC change --> MII still busy --> retry 3 times, then throw away --> OK
00:09   OPC change --> MII not busy anymore --> Send Notification --> OK
Reality
00:00   OPC change --> MII idle --> Send Notification --> OK
00:03   OPC change --> MII busy --> retry 3 times, then throw away --> OK
00:06   OPC change --> MII still busy --> PCo does nothing --> BAD
00:09   OPC change --> MII not busy anymore --> PCo does nothing --> BAD
Best regards,
Martin