Additional instances of the Open Platform Communications (OPC) server

In order to address concerns over the Area of Responsibility (AOR) for RealTime data, you can create multiple instances of the Open Platform Communications (OPC) Server. This will enable you to limit the read and write access per instance, so that you do not inadvertently provide full read (and potentially write) access to all OPC clients.

Multiple instances of the OPC Server can be run on the same RealTime computer. With them, you can employ allowlists that will expose different subsections of the RealTime database (RTDB) per instance of the OPC Server. Each instance can have its own access levels, and clients using the OPC Server will be confined to the views of the RTDB that you have configured in the allowlists. For example, the record analog.blat can be configured to be readable and writable for one OPC Server, and read-only to a second OPC server. You can also make any instance of the OPC Server oblivious to a record’s existence by leaving it out of the instance’s allowlist.

Multiple instances are created by soft-linking the files in the OPC directory from bin to child. The configuration file is modified for each instance, making each unique. Multiple instances are set up by AVEVA personnel upon request.

Note: Additional instances have certain limitations when writing, even if the point is designated as writable. For example, writing a value to the curval of an analog record may only be feasible if the point is in manual mode.