Please explain what is the Difference Between OPC UA and OPC DA ?
In which condition which one should be used, and if any example can be provided for both OPC UA and OPC DA, it would be helpful
Because of the shift in data communication technology, the OPC UA protocol is not inherently backwards compatible with Classic OPC data access (DA) models. OPC DA servers require a UA Wrapper to access UA client applications.
What is OPC DA? OPC DA stands for OPC Data Access. It is an OPC Foundation specification that defines how real-time data can be transferred between a data source and a data sink (for example: a PLC and an HMI) without either of them having to know each other's native protocol.
OPC UA (short for Open Platform Communications United Architecture) is a data exchange standard for industrial communication (machine-to-machine or PC-to-machine communication).
OPC-UA is the successor to OPC-DA. It has many benefits, one of the most prominent being that it is platform agnostic. There are SDKs available in a multitude of languages and OPC-UA can be implemented on anything from a tiny embedded to device running Linux, to a desktop running Windows, or a server running the OS of your choice.
For any new development, given the choice, OPC-UA should be used. The only reason to use OPC-DA at this point in time is if you're connecting to a legacy product that only supports OPC-DA and cannot be replaced or upgraded.
OPC UA is not only for OPC-DA, but for all OPC Classic (DA, AE, HDA, etc). OPC Classic uses DCOM communication for Client-Server connection. DCOM is for Windows OS. And, DCOM and RPC ports are a headache for engineers.
So, OPC UA is new technology which does not rely on DCOM communication and is platform (OS) independent. OPC UA supports Linux as well.
A lot of OPC servers in the market are not ready for OPC UA. But I believe they are on the way.
OPC client application developers need to focus that your OPC client app supports for which OPCs? For which purpose, e.g. AE:alarm and event collection or DA:data access)
Every OPC knowledge are avaliable at https://opcfoundation.org/. You can download source codes and some component Dlls but you must be a member.
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