OPC Server Computer Recommended Settings - Step 2
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This section covers the DCOM settings for the OPC server computer that are specific to your OPC server.  You should already have the DCOM Config Utility running and go to the Applications tab. The settings shown here are OPC server specific and are done on the Applications Tab of the DCOM configuration utility.  We will make general statements here and specific recommendations about OPC server products from Software Toolbox.  The rule "know thy own OPC server" applies to these settings - consult the documentation for your OPC server for any DCOM settings recommended by your server vendor.. To set the OPC server specific settings, go to the Applications tab in DCOM Config and browse until you find the OPC server of your choice. Highlight it and either double click on it or click the Properties button to enter the server specific settings. Server Specific Properties: General Tab On the General Tab, we recommend that you leave the Authentication level to Default. This will mean that this server will use the method of determining who will be allowed access that was setup on the Default Properties tab in the DCOM Config utility. We do NOT recommend that you change this setting unless you know what you are doing or are directed to by one of our support engineers. Server Specific Properties: Location Tab Make sure that the Run application on this computer is the ONLY check box checked. The Run application on the computer where the data is located check box should NOT be checked, and the Run application on the following computer should NOT be checked. This is the only valid configuration for OPC servers that we have worked with before. Server Specific Properties: Security Tab 1. We suggest you select "Use Default Access Permissions", which will mean users/groups shown under Default Access Permissions on the Default Security tab in the DCOM Config utility will have access to connect to this specific OPC server. Understand that if you select "custom" and put no groups/users into the list, then no client, local or remote, will be able to connect. So if you choose to use the custom permissions to override the defaults, know which users/groups you wish to grant permission to. 2. We also suggest that you use the Default Launch Permissions, which will mean users/groups shown under Default Launch Permissions on the Default Security tab in the DCOM Config utility will have access to launch this specific OPC server. The same rules apply about using custom launch permissions here as they do for custom access permissions - use with care and know what you are setting.  If you use custom and set nothing, no users will be able to launch your OPC server. 3. Nearly every OPC server we have every seen sets up Custom Configuration Permissions by default - it is our recommendation that you do not modify these unless instructed by the OPC server documentation or the OPC server vendor's support staff. If instructed to change these, seek to understand "why", as these permissions do not normally affect simple OPC client/server connections. Server Specific Properties: Identity Tab On the Identity tab, you specify under what user account you want the OPC server to run under.  This is probably one of the MOST important settings for the OPC server in some cases. The answer is very dependent on HOW you will be using your system. 1. If you will NOT have anyone logged onto the machine where the OPC server is running, then do NOT use the Interactive user.  The reason is that if you did, and a remote client tried to launch the server, and on one was logged in on the OPC server computer, there would be no "interactive user" logged in to start the OPC server process under, thus it would fail to start.  In this case we recommend that you try and run the OPC server as a service under the System account if that is an option with the OPC server you are using, otherwise use a named user. 2. If a user will always be logged in on the machine where the OPC server is running, then you may use the Interactive User because that means there will be an "interactive user" under which to run the OPC server process. 3. We do NOT recommend using the Launching user as this will result in multiple copies of the same OPC server being started when multiple OPC clients connect. Software Toolbox OPC Server Specific Comments: Use defaults above with the following exceptions. TOP Server: If running without any user logged in on the OPC server computer, we recommend that you run the server as a service - this is done by clicking on Tools->Options from the TOP server.  We recommend that you run as the System account so that through the NT/2000 services applet you will be able to control whether or not the server is visible from the desktop when someone does login to the computer where the OPC server is running. We allow either method - do what is best for your needs in terms of visibility to the user of the OPC server running as a service. INGEAR OPC Servers: Running as a service is not available, so if you will not have someone logged into the computer when remote clients are connecting (i.e no OPC client running on the machine where the OPC server is located), we recommend running as a named user who has appropriate rights to Launch the OPC server. Server Specific Properties: Endpoints Tab - No changes required on this tab.

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