When the Serverwants to provide the overall health status of an asset over time, the history of the 2:DeviceHealth Variableshall be used. For each 2:DeviceHealth Variable, where the history is currently tracked, the Historizing Attributeis set to True and the AccessLevelis set to HistoryRead. In order to provide the information, when history tracking started, a HistoryDataConfigurationis referenced with a HasHistoricalConfiguration Reference(see OPC 10000-11for details).

When the Serverwants to provide information for tracking the alarms with detailed health information of an asset over time, the history of the events based on the alarms shall be used. . This specification does not define which Objectsare used as EventNotifier. As defined in the base specification, the Server Objectshall be an EventNotifierwhen events are supported, which can be used to subscribe to all events of the Server. It is, therefore, server-specific where the history of events can be accessed and what details of the events are stored. The general concepts are defined in OPC 10000-11. The server should provide for each asset the history of events for the same amount of time as the history of the 2:DeviceHealth.