The dualized server solution protects your system against a server failure, which invariably results in loss of data. Both the primary server and the secondary server have direct connections to the PLCs in the system and collect the same data. The dualized server solution thus requires PLCs that support two simultaneous connections.
Both servers operational
In this mode both servers are updated with data from the PLCs. The operator stations can connect to either of the servers and control the process as in a stand-alone server system. The System Configuration program allows the user to define which server should be the primary server for each operator station. The workload involved in updating the operator stations can thus be shared by the two servers.
Only one server operational
If one server fails, the operator stations will automatically switch to the operational server and normal process control is continued. When the faulty server is brought back online, it can request the data collected during the downtime period from the other server. The operator stations that were switched to the online server can be configured to automatically switch back to the restored server.
Synchronization of local data between the two servers
Operations that do not require any communication with a PLC are local to each server in a dualized system. These local objects can also be synchronized between the servers.
Synchronization between Server and Hot Stand-by Server
IGSS now offers a mechanism for automatic synchronization of object status, alarm status and alarm inhibit status on local objects.
This is done by adding a synchronizer application to the system which connects to both servers and routes local object information between the servers. Prior to this new application, all synchronization between servers had to be done “through the PLC”.