OPC UA enables Servers, Clientsand networks to be redundant. OPC UA provides the data structures and Servicesby which Redundancymay be achieved in a standardized manner.

Server Redundancyallows Clients to have multiple sources from which to obtain the same data. Server Redundancycan be achieved in multiple manners, some of which require Client interaction, others that require no interaction from a Client. Redundant Serverscould exist in systems without redundant networks or Clients. Redundant Serverscould also coexist in systems with network and Client Redundancy. Server Redundancyis formally defined in 6.6.2.

Client Redundancyallows identically configured Clients to behave as if they were single Clients, but not all Clients are obtaining data at a given time. Ideally there should be no loss of information when a Client Failoveroccurs. Redundant Clientscould exist in systems without redundant networks or Servers. Redundant Clientscould also coexist in systems with network and Server Redundancy. Client Redundancyis formally defined in 6.6.3.

Network Redundancyallows a Client and Serverto have multiple communication paths to obtain the same data. Redundant networks could exist in systems without redundant Serversor Clients. Redundant networks could also coexist in systems with Client and Server Redundancy. NetworkRedundancyis formally defined in 6.6.4.