Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 1.20, 2.00, 2.01

Question: Exactly how does Citect handle Trend server redundancy? 

Citect Trend Server redundancy operates in a Primary/Standby configuration. When both Trend Servers are running, the Trends are processed on both servers in parallel, and both written to disk. Because of this, each server must write to its own disk or private area on the file server. The Trend data is synchronised between the Primary and Standby servers in the following way: On startup, the Trend server will try to connect to the other Trend server. If it can connect, it will then transfer all the trend data from the last time it was shutdown to the current time.

You can only configure two Trend servers in a Citect project, the Primary server and Standby server. Citect Clients either talk to the Primary or Standby Trend server. On startup, they will try to talk to the Primary. If the Primary is not running, they will try the Standby. If the Primary comes back online, any Clients talking to the Standby will stay talking to the Standby server. (It does not matter which Trend server the clients talk to as they both contain the same data.) Allowing Clients to attach to either server will help balance the load generated by each client on the server.