Attempts to configure an ArcGIS Data Store fails and the following error message is returned:
Error: The specified ArcGIS Server already has a managed data store.
ArcGIS Server fails to register ArcGIS Data Store if a previous Data Store has been uninstalled from the server. Additionally, the previous data store connection remains active when viewed in ArcGIS Server Manager.
When uninstalling ArcGIS Data Store, the connection string is retained in the 'arcgisserver' folder under the dsconnections.lst file if Data Store is not unregistered prior to uninstalling. ArcGIS Server Manager automatically detects the connection string of an active data store and returns the error when attempting to configure a new data store with the server.
For more information, refer to ArcGIS Help: Uninstall ArcGIS Data Store.
As there may be multiple registered databases, the dsconnections.lst file may contain several database connection strings. Prior to deleting a specific data store connection, identify the ID of the database in question via the dataItem.json file. The instructions provided describe how to remove the data store connection from the dsconnection.lst file located in the 'arcgisserver' folder: