This book introduces how to transfer data between applications or companies by using XML technique, It is considered to be the best technique that enables indexing mechanisms to data exchange. The introduced method can be efficient and easy to implement, in addition, it has low complexity and can make different operations. In this book XML file generated and retrieved in three types of database management system (Oracle, Access and SQL server). In order to achieve a data transfer between heterogeneous data sources i.e if the file is generated in oracle it would be read XML content in SQL server and stored the data in table, so it could transfer heterogeneous data from oracle to SQL server and vise versa.