This asynchronous function asynchronously 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 function 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 ReadComplete event handler.
Overload List
| Overload | Description |
|---|---|
| ReadRaw(Int32,OPCHDAtime,OPCHDAtime,Int32,Boolean,Int32[],Int32,Int32[]) | This asynchronous function asynchronously 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 function 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 ReadComplete event handler. |
| ReadRaw(OPCHDAtime,OPCHDAtime,Int32,Boolean,Int32[],OPCHDAitem[],Int32[]) | This synchronous function reads the values, qualities, and timestamps from the history database for the specified time domain for one or more items. When 'bounds' is TRUE, the bounding values for the time domain are returned. This function 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. |
Requirements
Target Platforms: Windows 7/8/10, Windows Server 2008/2012/2016, .NET 4.x