OPC UA Serversthat are part of a Redundant Server Sethave certain AddressSpacerequirements. These requirements allow a Client to consistently access information from Serversin a Redundant Server Setand to make intelligent choices related to the health and availability of Serversin the Redundant Server Set.

Serversin the Redundant Server Setshall have an identical AddressSpaceincluding:

The only Nodesthat can differ between Serversin a Redundant Server Setare the Nodesthat are in the local Servernamespace like the Server diagnostic Nodes. A Client that fails over shall not be required to translate browse paths or otherwise resolve NodeIds. Serversare allowed to add and delete Nodesas long as all Serversin the Redundant Server Setwill be updated with the same Nodechanges.

All Serversin a Redundant Server Setshall be synchronized with respect to time. This may mean installing a NTP service or a PTP service.

There are other important considerations for a redundant system regarding synchronization: