Open Platform Communications (OPC) DA client and server connection

In order to connect to an Open Platform Communications (OPC) server, your client application must specify both a computer hostname and an OPC server name. The default AVEVA Enterprise SCADA OPC server name is OASySDNA.OPCDAserver.1 or OASySDNA.OPCDAserver (the version independent name).

For hostname selection, you must specify the virtual RealTime hostname. For example, you have redundant RealTime computers named primaryRTS1 and primaryRTS2, and the virtual RealTime hostname is primaryRealTime. Your client should always connect to the host named primaryRealTime. This ensures that your connection is always made to the hot and operational RealTime OPC server.

Note: While many clients allow you to browse for all servers on a specified computer, the virtual RealTime hostname will not show up this way. You must enter it in explicitly.

If you are having connectivity problems, first verify that the OPC server is running on the hot RealTime computer. Any subsequent problems can probably be traced to DCOM issues.

Note: If a client is connected during a RealTime failover, the client will be required to reconnect. This is because the OPC Server they were connected to went on standby, so the client must establish a connection to the newly hot computer.

The following web pages cover DCOM security settings and issues in detail:

OPC and DCOM Security

OPC DCOM White Paper

Software Toolbox DCOM Tutorial

DCOM - Secure by Default

Quick Start Guide: Remote OPC DA (DCOM)