This method reads the values, qualities, and timestamps from the history database for the specified time domain for one or more items. When bBounds is TRUE, the bounding values for the time domain are returned. This method is intended for use by clients wanting the actual data saved within the historian. The actual data may be compressed or may be all data collected for the item depending on the historian and the storage rules invoked when the item values were saved. The optional bounding values are provided to allow clients to interpolate values for the start and end times when trending the actual data on a display.
Overload List
| Overload | Description |
|---|---|
| ReadRaw(DateTime,DateTime,Int32,Boolean,Int32[],OPCHDAItem[],Int32[]) | Synchronous ReadRaw. This method reads the values, qualities, and timestamps from the history database for the specified time domain for one or more items. When bBounds is TRUE, the bounding values for the time domain are returned. This method is intended for use by clients wanting the actual data saved within the historian. The actual data may be compressed or may be all data collected for the item depending on the historian and the storage rules invoked when the item values were saved. The optional bounding values are provided to allow clients to interpolate values for the start and end times when trending the actual data on a display. |
| ReadRaw(Int32,DateTime,DateTime,Int32,Boolean,Int32[],Int32,Int32[]) | Asynchronous ReadRaw. This method reads the values, qualities, and timestamps from the history database for the specified time domain for one or more items. When bBounds is TRUE, the bounding values for the time domain are returned. This method is intended for use by clients wanting the actual data saved within the historian. The actual data may be compressed or may be all data collected for the item depending on the historian and the storage rules invoked when the item values were saved. The optional bounding values are provided to allow clients to interpolate values for the start and end times when trending the actual data on a display. The results are returned via the client's IOPCHDA_DataCallback::OnReadComplete method. |
Requirements
Target Platforms: Windows XP Professional, Windows Server 2003 family, Windows Vista, Windows 7, Windows Server 2008 family