Historical Access Overview

Historical Access is based on the original OPC HDA specification and adapted to leverage the full benefits of OPC UA and are defined in UA Specifications Part 11 - Historical Access.

Intended for processing and analyzing data collected from a PLC/controller and/or OPC DA Server.

In addition to historical data, the UA version of this specification introduces the ability to obtain and process historical events information too.

This technology provides the following capabilities:

Capability

 Description

Read

Obtain the history of 1...n Nodes in a single call.

The request can specify numerous parameters such as the start/end dates, along with any statistical functions to invoke such as the Average, Min, Max, and many, many other Aggregates.

Update

Update the information stored in a database for 1...n Nodes in a single call.

The request can specify the action, such as delete, update, or create new historical records.

Subscription

The ability to request a Server to monitor Nodes and to send a notification to the Client when the value changes. Additional filters can be imposed such that the server can use an aggregate such as Average and notify the client when values change etc.

There are many other features of Unified Architecture that are inherited by the Historical  Access profile.

There are 4 demonstration applications available: