OPC Studio User's Guide and Reference
Multiple Implementations
For OPC Data Access, OPC Data Client actually contains two implementations of the low-level client code (the code that actually handles the OPC operations). They are:
As you can see, each implementation has its advantages and disadvantages. By default, both implementations are enabled, and OPC Data Client chooses the appropriate implementation.
In this default state, the decisions about which client code gets used are made as follows:
You can enable or disable the individual client implementations using following parameters in InstanceParameters Property of the EasyDAClient:
If you modify these properties, you need to do so before first OPC operation on that instance of the client object.
By leaving just one client implementation enabled, you can force that instance of EasyDAClient to always use the selected implementation.
Besides the main differences in the implementations (listed above), there are of course numerous less important behavior differences between them. The higher layers in OPC Data Client attempt to hide many of these differences to the extent that is practical, but obviously, precise 1:1 correspondence cannot be achieved.
For OPC Alarms&Events, OPC Data Client contains two implementations of the low-level client code (the code that actually handles the OPC operations). They are:
Each implementation has its advantages and disadvantages. By default, both implementations are enabled, and OPC Data Client chooses the appropriate implementation.
In this default state, the decisions about which client code gets used are made as follows:
You can enable or disable the individual client implementations using following parameters in InstanceParameters Property of the EasyAEClient:
If you modify these properties, you need to do so before first OPC operation on that instance of the client object.
By leaving just one client implementation enabled, you can force that instance of EasyAEClient to always use the selected implementation.
Besides the main differences in the implementations (listed above), there are of course numerous less important behavior differences between them. The higher layers in OPC Data Client attempt to hide many of these differences to the extent that is practical, but obviously, precise 1:1 correspondence cannot be achieved.