Redundancy and methods
There are two options for configuring redundancy:
- The primary and secondary OPC UA Connectors are connected to the same OPC UA Server.
- The primary and secondary OPC UA Connectors are connected to different OPC UA Servers.
In both cases, one OPC UA Connector is active and the other is in a standby state as a warm backup. Both OPC UA Connectors run independently of each other and do not communicate or synchronize their operations. The OPC UA Servers must implement any necessary synchronization if needed.
When both OPC UA Connectors are connected to the same OPC UA Server, each OPC UA Connector runs in a separate session with the OPC UA Server. The OPC UA Server, not the OPC UA Connectors, determines whether an operation that runs in one session is visible to the other session.
When both OPC UA Connectors are connected to different OPC UA Servers, the OPC UA Servers must explicitly implement synchronization between servers.
A method request is only sent to the active OPC UA Connector. The standby OPC UA Connector does not receive method requests. When the standby OPC UA Connector becomes active, it will not present the correct state for any outstanding methods. The OPC UA Server may complete previously requested methods, but the OPC UA Connector will not return the success or failure results to the requesting
FactoryTalk
software.The use of methods should be limited to configurations with a singular or non-redundant OPC UA Connector and OPC UA Server.
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