In the DeltaV system, when you set up a pair of Application Stations to run a redundant subsystem, the specified Application Station name is used as the Windows workstation name for one of the Application Stations and the characters _S are appended to this name for use as the Windows workstation name of the other Application Station.
For example, if the Application Station name you specify is AppStat, the Windows workstation names of the physical pair of Application Stations will be AppStat (user-specified) and AppStat_S (system-generated). At any given point in time, due to switchover sequencing, the active subsystem may be running on either physical Windows workstation, AppStat or AppStat_S. However, in the DeltaV system, the Application Station pair is always referred to with the logical name AppStat.