Tips & practical notes

Tips and practical notes for operating the OPC DA connector.

This page collects tips and practical notes for operating the OPC DA connector through the EnlyzeDA Gateway and the OPC DA protocol.

DCOM configuration

OPC DA builds on COM/DCOM. When the EnlyzeDA Gateway accesses an OPC DA server that runs on another machine, that communication goes over DCOM. In our experience, DCOM is the most common source of errors when connecting via OPC DA.

Pay attention to the following points:

• Permissions: The user account the gateway runs under needs the DCOM access and launch permissions for the server on the OPC DA server machine.

• Firewall: Besides the endpoint mapper on port 135, DCOM uses a dynamic port range. Both must be reachable between the gateway machine and the OPC DA server.

• Same machine as the simplest case: If the gateway runs on the same Windows machine as the OPC DA server, cross-machine DCOM configuration is not needed. This is the most robust setup.

The EnlyzeDA Gateway and the DCOM permissions are set up together with ENLYZE. The ENLYZE team supports you with any configuration questions.

Slow OPC DA servers

OPC DA servers often run on older Windows machines and respond slowly depending on load. This shows up in two places:

• Variable Discovery: Reading out all available variables can take several minutes. For large servers, plan accordingly and wait for the discovery to finish.

• First data values: Some servers only deliver meaningful values after a few read cycles, while they fill their internal caches. It is therefore normal if no data appears immediately after the connection is established.

If a server never delivers meaningful values, check with the ENLYZE team whether the correct DA server name is set and the server is reachable.

Determining the DA server name

If it is not known under which name the OPC DA server is registered, ENLYZE can use the EnlyzeDA Gateway to list the OPC DA servers available on the machine. The name corresponds to the program ID (ProgID) of the server in the COM system. Alternatively, the manufacturer of the supervisory system can tell you the ProgID directly.

If you have any questions, feel free to contact us at [e-mail].