An OperationalDataStore is a database used by one or more applications to provide just enough data and just enough history of the data to operate correctly.

An OperationalDataStore may use the data model of the SourceSystem, the DataWarehouse, or an independent ThirdNormalForm.

An ideal is to use a StarSchema that matches the DataWarehouse. Then an OperationalDataStore is the "current edge" of the DataWarehouse history, and data ages from one or more SourceSystem back to the OperationalDataStore and then to the DataWarehouse.

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I would suggest an Historical Data Store, a frozen (near-line) database (as opposed to off-line), still available for data mining. - JohnPeterson