As a general rule, do not specify an Application Station name that ends with the characters _S. When the DeltaV system creates a pair of Application Stations for redundant DeltaV OPC Data Access Server, it appends these characters to whatever name you specify as the base name for the Application Station. Having a pair of Application Stations named nodename_S and nodename_S_S could result in misleading or undesirable results while working with redundant DeltaV OPC Data Access Server.
You cannot enable redundant DeltaV OPC Data Access Server on a pair of Application Stations if you have already enabled any other subsystems, such as Batch Executive, Batch Historian, Continuous Historian, Campaign Manager, Alarms and Events, or Remote Network, for the existing Application Station. To enable redundant DeltaV OPC Data Access Server on a pair of Application Stations, you must first disable any previously-enabled subsystems for this Application Station.
If you ever need to reconfigure either workstation in the pair, you should respond to this prompt by clicking Yes if it is the Application Station that you specified as the preferred active; otherwise, click No, if it is the workstation with the characters _S appended to the base Application Station name.