A HotAndMirrored Failovermode is where a Clientonly connects to one Server in the Redundant Server Setbecause the Serverwill share this session/state information with the other Servers. In order to validate the capability to connect to other redundant Serversit is allowed to create Sessionswith other Serversand maintain the open connections by periodically reading the ServiceLevel. A Clientshall not create Subscriptionson the backup Serversfor status monitoring (to prevent excessive load on the Servers). This mode allows Clientsto fail over without creating a new context for communication. On a Failoverthe Clientwill simply create a new SecureChannelon an alternate Serverand then call ActivateSession; all Clientactivities (browsing, subscriptions, history reads, etc.) will then resume. Figure 32illustrate the behaviour a Client would perform when communicating to a Server in HotAndMirrored Failovermode.

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Figure 32– HotAndMirrored Failover

This Failovermode is similar to the transparent Redundancy. The advantage is that the Clienthas full control over selecting the Server. The disadvantage is that the Clientneeds to be able to handle Failovers.