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[KB1118]MailBox error function MsgSend

Tags: Memory, Memory leak

4 years ago
By LM
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Applies to:

PcVue 11 onwards


Symptom:

In the event viewer you get this message:
“MailBox error: function MsgSend”
It can appear hundred times. It means that at least one manager is no more available. Unfortunately the concerned manager is often unknown.
This article will give some advices to find the manager causing this error.


Details:

If you have rights to acess to the Audits and Diagnostics dialog box, available since PcVue version 11, then you can display the monitoring tab in order to see which manager is saturated (“Pending in mailbox” counter value must be very high):
Pending in mailbox

Thanks to the Application Explorer, you can also add some system variables in order to monitor that information in the project:
PendingInMailbox system variables
If you don’t have this possibility you can find the information in Audit files by searching “pending” keyword. You will probably find some big values for some managers and it gives some clues to fix the issue:

Pending UI manager sample

In the same Audit file, if we look forward we can see that flow regulation is activated for LON and BACnet protocols. We also observe that there are many pending messages and many lost transitions:

Flow regulation

 

It is important to note at what time the problem appears.
In this specific case it was always during the night. Looking at the traces and audit files we could conclude that the network was disrupted during the night. It generates a lot of alarms, then a lot of Scada Basic treatments, then memory consumption increases, then a crash.
In this picture we can see the relations between several audit counters:
Relation between UI mailbox and memory usage

 



Created on: 01 Jul 2021 Last update: 30 May 2024