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Designated historian

More than one historian can write in the same profile, but exactly one of them answers long-range tag and history queries. Enable Designated tag historian reader on that one component and leave it disabled on the others.

flowchart LR
    subgraph Profinity["Profinity"]
        Tags --> Historian["Designated historian"]
    end
    subgraph Store["Database"]
        History["Tag history"]
    end
    Historian --> History
    History --> Queries["History queries"]
Tag history is written by each historian, and long-range history queries are answered from the store of the historian that has Designated tag historian reader enabled

If no component is designated, or more than one is, Profinity has no store to read history from and does not answer long-range queries. An InfluxDB historian is designated only while its Allow Retrieval setting is also enabled. The setting is described on the page of each historian: InfluxDB historians and TAG SQL Historian.

To set up logging, refer to How to configure data logging.