Configuration HubSpecial Considerations for Enhanced Failover
If using Enhanced Failover, you must be in Maintenance Mode before you log to Configuration Hub. Maintenance Mode allows you to temporarily suspend synchronization between the two SCADA nodes in an Enhanced Failover pair. This allows you to add or modify groups and tags in your iFIX database while the Scan, Alarm, and Control (SAC) program is running. When you enter Maintenance Mode, SCADA synchronization temporarily stops; synchronization between the SCADA pair is suspended. After Maintenance Mode is enabled, you can make changes to the database on the primary node.
Configuration Hub will not allow you to make changes unless the primary node you are configuring is in Maintenance Mode. It will also not allow any configuration on the Secondary node (you cannot login). All changes to a Failover pair in Configuration Hub must be made on the Primary node.
Every time you make a change in the configuration and publish, the data is reloaded in the configuration and the driver is restarted. This is important to know if you are making changes on a live system. You will NOT need to restart iFIX after you make any changes in the Configuration Hub. However, after you exit Maintenance Mode, you will need to stop and restart the driver from Mission Control on the secondary in order to pick up the configuration changes
Deleting Servers or Groups
Be aware that when the iFIX SCADA Enhanced Failover pair has the OPC UA Driver configured, any server or group delete operation in the Configuration Hub UI on the Primary will not be deleted on Secondary after the maintenance mode synchronization happens. The Secondary SCADA continues to retrieve data since the server and/or group still exist on the Secondary. As a workaround, manually delete the server and group files from the secondary SCADA, since you cannot run Configuration Hub on the secondary SCADA.
Server and Group configuration files are found in the PDB\iFixUaClient folder, in Servers and Groups folders, respectively. Each server and group has its own file. In each of these folders, compare the contents on the Primary node to those on the Secondary. If a file exists on the Secondary but not on the Primary then open the file in a text editor and verify that it is a server or group that was deleted from the Primary. If so, delete that file from the Secondary.
For all other operations, the synchronization works as expected such as: Server Create, Driver tag deletions or updates, Group updates, and so on.
Notes on Certificate Management
When the iFIX SCADA is part of an Enhanced Failover pair and we have enabled the OPC UA Driver on the SCADA, each physical SCADA needs to establish trust with the configured OPC UA Server separately. After both SCADAs can communicate to a remote OPC UA Server individually using their certificates, you can then bring the iFIX SCADAs up as failover pair. Be sure to confirm that you can communicate individually first.
Special I/O Addresses
There are special I/O addresses in iFIX that are very helpful in a Redundancy Configuration for the OPC UA Client. Using the ConnectionStatus and EndpointUrl addresses, you can see the overall connected status of a (logical) server, and the endpoint it is currently using for data.