Hello.

The capacity can be changed by setting the CallbackQueueCapacity property of the EasyUAClient object. It must be done before any OPC operation is invoked, otherwise it will have no effect.

The error indicates that the OPC UA notifications are coming in with faster rate than your code is able to process. For example, if there is a steady stream of notifications (events or callbacks) with average period 10 milliseconds, but your code takes 20 milliseconds to process each notification, the queue will grow and grow and eventually fill up, which is what the error is indicating.

The default setting (100000 notifications) makes room for quite a big "lag" in your processing already. Unless the problem is in a short-time peak (that would eventually be consumed and processed), increasing the capacity will just delay the occurrence of the error, but will not resolve the problem.

Best regards