Use RDSConnection to specify the RDS connection component to use to obtain the recordset when the TADODataSet is opened. This property is mutually exclusive of the Connection property. If the TADODataSet uses RDSConnection to connect to the default RDS DataFactory, then the ConnectionString property should also be set with the connection information required by the DataFactory. The CommandText property should either specify the name of a property on the associated business object or be an SQL query. 

TRDSConnection 

Using TADODataSet