For non-transparent Redundancy, OPC UA provides the data structures to allow the Client to identify what Serversare available in the Redundant Server Setand also Serverinformation which tells the Clientwhat modes of Failoverthe Serversupports. This information allows the Clientto determine what actions it may need to take in order to accomplish Failover. This information is specified in NonTransparentRedundancyType ObjectTypedefined in OPC 10000-5.

Figure 27shows a typical non-transparent Redundancysetup.

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Figure 27– Non-Transparent Redundancy setup

For non-transparent Redundancy, the Serverswill have unique IP addresses. The Serveralso has additional Failovermodes of Cold, Warm, Hotand HotAndMirrored. The Clientshall be aware of the Redundant Server Setand shall be required to perform some actions depending on the Failovermode. These actions are described in Table 111and additional examples and explanations are provided in 6.6.2.4.5.2.for Cold, 6.6.2.4.5.3for Warm, 6.6.2.4.5.4for Hotand 6.6.2.4.5.5for HotAndMirrored.

A Client needs to be able to expect that the SourceTimestamp associated with a value is approximately the same from all Serversin the Redundant Server Setfor the same value.