Configure OPC HDA Server-Specific DOCM Settings

Historian OPC HDA Server supports DCOM (Distributed Component Object Model) to browse the Historian OPC HDA Server remotely. If you want to grant only certain users permission to launch or access the remote Historian OPC HDA Server, you can use the Windows utility, DCOMCNFG.EXE for configuring DCOM applications. DCOMCNFG.EXE is usually located in your operating systems \system32 folder.

When OPC Servers register, they set up initial custom DCOM security settings to enable users on the network to access and launch the Server. On large networks, it is recommended that you modify these settings to avoid confusion and inadvertent changes to a running OPC Server. If Firewall security is enabled on Windows XP or Vista, you must also modify or add items to the Exceptions list. See Setting Up the Windows XP or Vista Firewall for Use with Remote OPC Servers.

Note: Following are a few notes to keep in mind:
  • It is recommended that all users that need to access remote OPC Servers be members of the Administrators group. To facilitate this, It is recommended creating a users group to contain individual users who need to access remote OPC servers.
  • To make any OPC HDA Client / OPC HDA Server application work via DCOM, changes need to be made on both sides, especially if you intend to use Asynchronous I/O communications.
  • OPCENUM must reside on the remote machine with the OPC server. While most OPC Server applications install and register this file, some do not. You can download this file from www.opcfoundation.org. Currently, it is contained within the OPC Core Components 2.00 Redistributable 2.30.msi file. After you download OPCENUM, run the .msi file.
  • This section applies to OPC HDA servers that need to use DCOM communications, regardless of whether the OPC server uses Serial or Ethernet devices.
  • If OPC communications is confined to a single machine (that is, using COM, but not DCOM), it continues to work properly without making changes to DCOM settings.
  • If Historian OPC HDA Server and OPC HDA Client are on same machine, then you do not need to change your DCOM settings.
  • If this is the first time you are connecting to (or allowing connections from) other machines on the network, you must run the Windows Network Wizard (from Start > Control Panel) to set up your computer to run on your network. This allows you to share resources on your computer with other computers on your network. It is recommended that you run the Network Setup Wizard before modifying the DCOM settings.