Cause

0x80040202 error appears in the OPC Client (ibaPDA; during the apply checks) application when it fails to receive a callback from the OPC Server.

Symptoms

When an OPC Client application is unable to receive callbacks from an OPC Server, users will notice at least two symptoms:

1. The OPC Client application will fail to create an OPC Group altogether.

2. The OPC Client application will not be able to show data updates. Instead, data values will remain unchanged.

In the ibaPDA IO-manager you will be able to connect to the OPC server and add signals, however during the apply of the configuration you will receive the 0x80040202 DCOM error.

Background

OPC supports a report-by-exception (RBX) mechanism whereby the OPC Server sends data updates to the OPC Client (such as an HMI, Historian, APC, ERP, etc.) whenever the data changes (also known as "on data change"). OPC terminology refers to this mechanism as "subscription". OPC Servers are able to achieve subscription updates through the use of asynchronous callbacks. In other words, when the OPC Server detects a change in the data, it immediately "calls" the client back with the data update. This is an asynchronous mechanism because the OPC Client does not know when the OPC Server will send the data. However, if you don’t set the security settings properly, these data updates will fail. OPC Client applications typically indicate this failure by setting the Quality value of an item to "Bad".

Callbacks force an OPC Server to actively establish a connection with an OPC Client. In a sense, the OPC Server becomes a Client and the Client becomes a Server.

ibaPDA is using Async connections only

Test

One simple test to determine whether or not a callback is failing is to force the OPC Client to issue a "Synchronous Cache Read" or a "Synchronous Device Read". If either one of these return values with "Good" quality, then the lack of data updates is likely due to the OPC Server being unable to send callbacks to the OPC Client application.

Most likely you well need other 3rd party tools to perform this test, it can be configured in Matricon OPC Explorer. By default OPC explorer is using the Async read mode:

Solution

Give the ibaPDA machine the same rights as it was a OPC server. Seehe attachement, or consult the iba OPC manual.