DCOM clients and servers

OPC servers are DCOM servers, and OPC clients are DCOM clients, but the roles are not fixed.

PI Interface for OPC DA retrieves data from the OPC server using asynchronous callbacks. During a callback, PI Interface for OPC DA acts as a DCOM server, while the OPC server acts as a DCOM client. For this reason, DCOM security on the interface node must be configured to allow access by the account associated with the OPC server.