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In OPC, Is There A Difference Between Data Change, Report By Exception, and Unsolicited Data?


Last Update: 11/7/2018

No, these options all mean the same thing. For most OPC clients, the default setting is to connect to a server and then set all items being requested to an active and subscribed (or advised) state. When this occurs, the server will poll the devices for the data. If the items' values changed from the previous poll, the server will update the client with the new data. "No change" means no update, which greatly decreases the amount of traffic between the server and the client application.

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