The DeltaV OPC History Server incorporates all the required interfaces and methods of the OPC HDA Specification. It also incorporates the optional "ReadProcessed" method under the IOPCHDA_SyncRead interface.
The DeltaV OPC History Server provides a time stamp and quality value associated with each historical data value. For raw data values, the time stamp is the time the value was recorded by the DeltaV Continuous Historian. For processed data values, the time stamp is the start of the interval, with two exceptions, minimum and maximum, which can be requested with actual time stamps or interval time stamps. The OPC HDA quality value makes use of the parameter and collection status quality information that is available from the DeltaV Continuous Historian.
The DeltaV OPC History Server presents time to client applications in UTC. Client applications are responsible to make any necessary time stamp modifications (such as conversion to local time).