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6.3 ObjectTypes for the Server Object ToC Previous Next

6.3.8 TransparentRedundancyType ToC Previous Next index

This ObjectType is a subtype of ServerRedundancyType and is used to identify the capabilities of the OPC UA Server for server-controlled redundancy with a transparent switchover for the client. It is formally defined in Table 16.

Table 16 – TransparentRedundancyType Definition

Attribute Value        
BrowseName TransparentRedundancyType        
IsAbstract False        
References Node Class BrowseName DataType TypeDefinition Modelling Rule
Subtype of the ServerRedundancyType defined in 6.3.7, i.e. inheriting the InstanceDeclarations of that Node.          
HasProperty Variable CurrentServerId String PropertyType Mandatory
HasProperty Variable RedundantServerArray RedundantServerDataType[] PropertyType Mandatory

RedundancySupport is inherited from the ServerRedundancyType. It shall be set to TRANSPARENT_4 for all instances of the TransparentRedundancyType.

Although, in a transparent switchover scenario, all redundant Servers serve under the same URI to the Client, it may be required to track the exact data source on the Client. Therefore, CurrentServerId contains an identifier of the currently-used Server in the Redundant Set. This Server is valid only inside a Session; if a Client opens several Sessions, different Servers of the redundant set of Servers may serve it in different Sessions. The value of the CurrentServerId may change due to Failover or load balancing, so a Client that needs to track its data source shall subscribe to this Variable.

As diagnostic information, the RedundantServerArray contains an array of available Servers in the Redundant Set; including their service levels (see 12.7). This array may change during a Session.

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