Can OPC Expert be deployed in redundant or high availability OPC architectures, and how does its built-in failover capability work?
OPC Expert supports redundant architectures through built-in failover capability that can automatically switch to a secondary data source when the primary source becomes unavailable. This capability is included within OPC Expert and applies to tunneled connections as well as direct OPC connections. Engineers designing high availability systems can use OPC Expert to eliminate the OPC communication layer as a single point of failure.
How Built-In Redundancy Works
OPC Expert’s redundancy function connects to two OPC servers simultaneously, a primary and a standby. It continuously monitors the state of the primary connection and automatically switches to the standby when it detects a failure. The failover can be triggered by a loss of connection, by data becoming stale, or by a value exceeding a defined threshold. Once the primary source recovers, OPC Expert can be configured to fail back automatically, returning to the preferred source without manual intervention.
Redundancy Options Available
OPC Expert supports Hot, Warm, and Cold redundancy configurations. In a Hot redundancy setup, both the primary and standby servers are actively connected and monitored, which means failover is nearly instantaneous because no connection establishment delay is required. Warm redundancy keeps the standby connection ready but not fully active, while Cold redundancy initiates the standby connection only after a failure is confirmed. The appropriate option depends on how quickly a failover must complete and what the downstream application can tolerate in terms of data interruption.
Redundancy in Tunneled Deployments
The tunneling and redundancy capabilities within OPC Expert work together. A tunneled connection can be configured with a redundant source on the remote side, so that if the primary OPC server at the remote site becomes unavailable, OPC Expert automatically switches to the standby server and continues delivering data through the tunnel. The transition is managed internally and does not require the OPC client on the receiving end to take any action. From the client’s perspective, data continues to flow from what appears to be a single local OPC server.
Continuous Operation Through Windows Service Mode
OPC Expert can run as a Windows service, which means it starts automatically when the host machine boots and continues running without requiring a user to be logged in. This is an important characteristic for high availability deployments, because it ensures that the redundancy logic is active at all times and that a system restart does not create a window of vulnerability. The service mode also allows Windows to manage OPC Expert’s process, including restarting it if necessary.
Relevant Tools
OPC Redundancy, part of OPC Expert, provides the Hot, Warm, and Cold failover capabilities described above. OPC Tunneler, also part of OPC Expert, handles the cross-network communication layer and integrates with the redundancy function to support high availability in distributed architectures.
OPC Expert is well suited to redundant and high availability deployments. Its built-in failover capability, combined with the ability to run as a Windows service and its support for multiple redundancy modes, gives engineers the tools to design OPC communication architectures that keep data flowing even when individual components fail.