In an OPC UA Serverthat is implementing the A&C Information Modeland that is configured to be a redundant OPC UA Serverthe following behaviour is expected:

• The EventId is used to uniquely identify an Event. For an Eventthat is in each of the redundant Servers, it shall be identical. This applies to all standard Events, Alarmsand Conditions. This may be accomplished by sharing of information between redundant Server(such as actual Events) or it may be accomplished by providing a strict EventIdgenerating algorithm that will generate an identical EventIdfor each Event
• It is expected that for cold or warm failovers of redundant Servers, Subscriptionfor Eventsshall require a Refresh operation. The Clientshall initiate this Refreshoperation.
• It is expected that for hot failovers of redundant Servers, Subscriptionsfor Eventsmay require a Refreshoperation. The Servershall issue a RefreshRequiredEventType Eventif it is required.
• For transparent redundancy, a Servershall not require any action be performed by a Client.