When it has been enabled, this notification makes it possible for an APPN topology application to get asynchronous notifications of port operational state changes, and thus to reduce the frequency with which it polls for these changes. This notification is only sent when a appnPortOperState has transitioned to a value of 'active' or 'inactive'. This notification is sent whenever there is a appnPortOperState object transition to 'inactive' or 'active' state in the appnPortTable. This notification is only sent for row creation if the row is created with a value of 'active' for appnPortOperState. This notification is only sent for row deletion if the last value of appnPortOperState was 'active'. In this case, the value of appnPortOperState in the notification shall be 'inactive', since the deletion of a row indicates that the port is no longer active. The notification is more than a simple 'poll me now' indication. It carries both a count of port table changes, and the operational state itself. The count of changes allows an application to detect lost notifications, either when polling or upon receiving a subsequent notification, at which point it knows it must retrieve the entire appnPortTable again. Generation of this notification is controlled by the appnTrapControl object.