RdStatusChanged (_RdStatusChanged@4 in Stdcall convention) is optional. It is called by the D2000 KOM when changing the active instance of the D2000 KOM and when switching the redundancy. The callback procedure GetRdStateAndInstance is used to detect whether the KOM process is connected to HOT Server and it is an active instance.
Note: Function is called also when using tell command SET_ACT_INST, but the active instance does not change (i.e. process was active and remains still active). So, it is always necessary to determine whether the instance or the D2000 Server was switched or not by GetRdStateAndInstance.