You can define global level metadata available for all XML files. You must not define these metadata more than once per deployment.

<?xml version="1.0" encoding="UTF-8"?>

<entity-mappings 
  xmlns="http://java.sun.com/xml/ns/persistence/orm"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_1_0.xsd"
  version="1.0">

    <persistence-unit-metadata>
        <xml-mapping-metadata-complete/>
        <persistence-unit-defaults>
            <schema>myschema</schema>
            <catalog>mycatalog</catalog>
            <cascade-persist/>
        </persistence-unit-defaults>
    </persistence-unit-metadata>

xml-mapping-metadata-complete means that all entity, mapped-superclasses and embeddable metadata should be picked up from XML (ie ignore annotations).

schema / catalog will override all default definitions of schema and catalog in the metadata (both XML and annotations).

cascade-persist means that all associations have PERSIST as a cascade type. We recommend you to not use this feature.