This method initially retrieves data from the start time to the end time. After the initial response it periodically (every updateInterval) responds with an updateDuration amount of data. The time of the last value returned in the initial response is used as the start time for the first update. After that, the time of the last value returned in an update is used as the start time for the next update. The results are returned via the client's IOPCHDA_DataCallback::OnPlayback method. Playback is only supported in the forward direction. The domain of the initial request is defined by startTime, endTime, and numValues The value of startTime must be defined. If endTime is not specified (DateTime.MinValue), the request shall be for all data from the startTime for the requested number of values. Then further data shall be sent according to the updateDuration and updateInterval from the time of the last value returned. Implementation of the operation is server dependent.
Syntax
| Visual Basic (Declaration) | |
|---|---|
Function PlaybackRaw( _ ByVal transactionID As Integer, _ ByVal startTime As Date, _ ByVal endTime As Date, _ ByVal numValues As Integer, _ ByVal updateDuration As TimeSpan, _ ByVal updateInterval As TimeSpan, _ ByVal serverHandles() As Integer, _ ByRef cancelID As Integer, _ ByRef errors As Integer() _ ) As Integer | |
| C# | |
|---|---|
int PlaybackRaw( int transactionID, DateTime startTime, DateTime endTime, int numValues, TimeSpan updateDuration, TimeSpan updateInterval, int[] serverHandles, out int cancelID, out int[] errors ) | |
Parameters
- transactionID
- An identifier created by the client and passed to the server in this call. The server shall return this identifier along with the results of this call.
- startTime
- The beginning of the history period to be read.
- endTime
- The end of the history period to be read.
- numValues
- The maximum number of values returned for any item over the time range. If only one time is specified, this number specifies the extent of the time range.
- updateDuration
- The amount of time the update covers in.
- updateInterval
- The interval to send data for updates.
- serverHandles
- The list of processed server items to be retrieved.
- cancelID
- Place to return a Server generated ID to be used in case the operation needs to be canceled.
- errors
- Array of HRESULTs indicating whether the corresponding server handle was valid.
Return Value
HRESULTS success/error code.Requirements
Target Platforms: Windows XP Professional, Windows Server 2003 family, Windows Vista, Windows 7, Windows Server 2008 family