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IEC 62541-11-2020 pdf free download
IEC 62541-11-2020 pdf free download.OPC unified architecture — Part 11: Historical Access
Architecture unifiée OPC — Partie 11: Accès a l’Historique.
If a request is made requesting both ServerTimestamp and Source Timestamp and the Server is only collecting the Source Timestamp the Server shall return Bad_TimestampsToReturnlnvalid.
For HistoricalEventNodes, this parameter does not apply. This parameter is ignored since the entries returned are dictated by the Event Filter. See IEC 62541-4 for details.
4.4 Bounding Values and time domain
When accessing HistoricalDataNodes via the HistoryRead Service, requests can set a flag, returnBounds, indicating that BoundingValues are requested. For a complete description of the Extensible Parameter HistoryReadDetails that include Start Time, EndTime and NumValuesPerNode, see 6.4. The concept of Bounding Values and how they affect the time domain that is requested as part of the HistoryRead request is further explained in 4.4, also provides examples of TimeDomains to further illustrate the expected behaviour.
When making a request for historical data using the HistoryRead Service, the required parameters include at least two of these three parameters: startTime, endTime and numValuesPerNode. What is returned when Bounding Values are requested varies according to which of these parameters are provided. For a historian that has values stored at 5:00, 5:02, 5:03, 5:05 and 5:06, the data returned when using the Read Raw functionality is given by Table 1. In the table, FIRST stands for a tuple with a value of null, a timestamp of the specified Start Time, and a StatusCode of Bad_BoundNotFound. LAST stands for a tuple with a value of null, a timestamp of the specified EndTime, and a StatusCode of Bad_BoundNotFound.
In some cases, attempting to locate bounds, particularly FIRST or LAST points, may be resource intensive for Servers. Therefore, how far back or forward to look in history for Bounding Values is Server dependent, and the Server search limits may be reached before a bounding value can be found. There are also cases, such as reading Annotations or Attribute data where Bounding Values may not be appropriate. For such use cases, it is permissible for the Server to return a Status Code of Bad_BoundNotSupported.IEC 62541-11-2020 pdf free download.
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