Data Source - OPC HDA Historian

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OPC Historical Data Access, also known as OPC HDA, is used to exchange archived process data. This is in contrast to the OPC Data Access (OPC DA) specification that deals with real-time data. OPC technology is based on client / server architecture. Therefore, an OPC client, such as a trending application or spreadsheet, can retrieve data from an OPC compliant data source, such as a historian, using OPC HDA.

Similar to the OPC Data Access specification, OPC Historical Data Access also uses Microsoft's DCOM to transport data. DCOM also provides OPC HDA with full security features such as user authentication and authorization, as well as communication encryption services. OPC HDA Clients and Servers can reside on separate PCs, even if they are separated by a firewall. To do this, system integrators must configure DCOM properly as well as open ports in the firewall. If using the Windows firewall, users only need to open a single port.

To create a connection to an OPCHDA Historian, Right-click on the Data Sources group, then click “More”, and then select “OPCHDA Historian”.


To successfully retrieve data from an OPCHDA Historian, the following properties need to be set.


  • Name (String)
Name to identify the data source.
  • Server (String)
Location of the OPCHDA Server (Server Name or IP Address).
  • Database (String)
Name of the OPCHDA Database.
  • Username (String)
If required, add the username to connect to the OPCHDA Historian.
  • Password (String)
If required, add the password to connect to the OPCHDA Historian.
  • Convert to Null (Dropdown)
In some cases, OPCHDA Historians display different characteristics when storing null values. This dropdown allows the user to select when Flow must interpret null values coming from the Historian, default N/A.
  • Maximum Concurrent
Maximum concurrent connections that will be made to the OPCHDA Historian, default 20.
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