EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/orm.xml
Use the orm.xml file to apply the metadata to the persistence unit. This metadata is a union of all the mapping files and the annotations (if there is no xml-mapping-metadata-complete element). If you use one mapping orm.xml file for your metadata and place this file in a META-INF directory on the classpath, then you do not need to explicitly list it. The EclipseLink persistence provider will automatically search for this file (orm.xml)and use it.
If you use a different name for your mapping files, or place them in a different location, you must list them in the mapping-file element of the persistence.xml file, as shown here:
<persistence-unit name="EmployeeService"> <jta-data-source>jdbc/EmployeeServiceDS</jta-data-source> <mapping-file>META-INF/employee_service_queries.xml</mapping-file> </persistence-unit>