When it has been enabled, this notification makes it possible for an APPN topology application to get asynchronous notifications of link station operational state changes, and thus to reduce the frequency with which it polls for these changes. This notification is only sent when a appnLsOperState has transitioned to a value of 'active' or 'inactive'. This notification is sent whenever there is a appnLsOperState object transition to 'inactive' or 'active' state in the appnLsTable. This notification is only sent for row creation if the row is created with a value of 'active' for appnLsOperState. This notification is only sent for row deletion if the last value of appnLsOperState was 'active'. In this case, the value of appnLsOperState in the notification shall be 'inactive', since the deletion of a row indicates that the link station is no longer active. The notification is more than a simple 'poll me now' indication. It carries both a count of link station 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 appnLsTable again. Generation of this notification is controlled by the appnTrapControl object.