About the AVEVA Historian

The AVEVA Historian is a real-time relational database for plant data. The historian acquires and stores process data at full resolution and provides real-time and historical plant data together with configuration, event, summary, and associated production data to client applications on the desktop. The historian combines the power and flexibility of Microsoft SQL Server with the high speed acquisition and efficient data compression characteristics of a real-time system.

The AVEVA Historian appears to client applications as a Microsoft SQL Server. The AVEVA Historian database server receives SQL queries and then locates, processes, and returns the data.

In the AVEVA Historian, plant data is stored in special history "extension" tables. The historian surpasses the functionality of Microsoft Transact-SQL by providing time domain extensions that allow for more useful retrieval of time-series data from these tables.

For example, the extension tables support cyclic and delta retrieval. For cyclic retrieval, evenly spaced data at a specified resolution is returned. For delta retrieval, data is returned for each time the value of a tag changed.

The combination of normal SQL Server tables and the extension tables provides a powerful way to access meaningful data stored in the database. Since the historian is a relational database, queries can join data across multiple tables to retrieve data efficiently.

Some examples of database queries possible with the historian are:

• Average vibration of a motor each day over the last month.

• Annotation for a discrete tag that was made six months ago.

• The limit of an analog tag in the context of a normal production mode. The limit of the same analog tag in the context of an accelerated production mode.

• The values for 50 specified analog tags at a point in time when the value of x was greater than 10.

• The path to the storage location for a specific tag.

• 20 evenly distributed data values from the total values stored for an analog tag between 8:00 and 8:30 a.m. on September 12, 2004.

• All data values at 20 minute intervals from the total values stored for an analog tag between 8:00 and 8:30 a.m. on September 12, 2004.

• All values of an analog tag stored on January 8, 2004, where the value of the analog tag changed by 10 engineering units. The data for this analog tag was stored if the value changed by 5 engineering units.

• All values for tags associated with an event boiler trip on January 8, 2004.