This OPC UA Variable allows simple applications to trigger the scan process. Simple appications involve OPC UA Clients that are limited to Data Access functionality.
The scan is triggered by writing True to the Variable Value. The behaviour of the scan is defined by the parameters in the ScanSettings FunctionalGroup defined in 9.3.7. The Value of the Variable is changed back to False by the Server if the scan is stopped according to the ScanSettings. The Client can stop the scan by writing False to the Variable Value.
The write permission can be limited to one Client. OPC 10000-3 and OPC 10000-5 define capabilities to enforce this limit with Roles and RolePermissions. Roles can be limited to a single OPC UA Application.
The scan result is provided through the Variable LastScanData. Further restrictions for this simple mechanism are described for the Variable LastScanData.