Disclosed is a mechanism that can be implemented in database systems to support distributed transactions in heterogeneous systems. Once the transaction manager of a database system implements this mechanism, application developers and vendors can integrate new datasources into the transaction manager of the database system. This would simplify the application design and ensure the integrity of data and interactions. The interface and interactions between the transaction manager and external datasources (both structured and non-structured) conform to X/Open XA standards. Also disclosed is a technique to design the system catalogs for organizing the datasources and instances of the new datasources.