Allowing External Access to Historical Data

Bridging and Web API read Data Historian values through external data access. A Data Historian tag serves these requests only after you allow external data access for it. Otherwise, the request returns no value and the status Bad - License Disabled. External data access is not allowed by default, including for tags created in an earlier version, so a Bridging transaction that reads historical data returns no values until you allow access for each tag it reads. Learn more

Each tag that allows external data access counts toward the Data Historian Access entitlement of your license, so allow access only for the tags that Bridging or Web API must read. Learn more

To allow external access to historical data:

1. Open Workbench, and in Project Explorer, expand My Project > Historical Data > Data Historian > Logged Data.

2. Do one of the following:

   • To allow access for every tag in a folder and its subfolders, right-click the folder and select Allow External Data Access for all tags.

   • To allow access for a single tag, right-click the tag and select Allow External Data Access.

   You can also select External Data Access on the General tab of a tag, calculated tag, or merge tag, and then click Apply. For a tag logged from an asset, the same option is on the equipment property or equipment class property on the Historical Data tab.

   To withdraw access, use Deny External Data Access for all tags on a folder, or Deny External Data Access on a tag.

3. Run the Bridging transaction or Web API request again. The request returns the logged values instead of Bad - License Disabled.