Data class will return Datasets, Scalars, ExecuteNonQueries, etc.... (This class does not know about the database, tables nor its' contents) It is generic enough to be ported over to any application, Web or Desktop, your PC or your friends' PC.
Business class will contain Sql statements, calculations and logic specific to your project. This class will Inherit the Data class.
The DataAdapters, connections are all in the Data class, they are created and destroyed as needed, nothing is global in my scenario.