When attempting to delete a data store item in Portal for ArcGIS, the following error message is returned:
Error: Unable to delete item. This data store item is registered in at least one server. Go to the Settings tab of this data store to deselect all federated servers.
The data store item is stored on a federated server.
Remove the federated server from the data store before deleting the data store item. Refer to Portal for ArcGIS: Add or remove from a federated server for instructions.