<hibernate-configuration>
    <session-factory name="HibernateSessionFactory">

      <property name="hibernate.current_session_context_class">jta</property>
      <property name="hibernate.transaction.factory_class">
           org.hibernate.transaction.JTATransactionFactory</property>
           <property name="jta.UserTransaction">UserTransaction</property>
          <property name="hibernate.transaction.manager_lookup_class">
           org.hibernate.transaction.WebSphereExtendedJTATransactionLookup</property>
      <!--property name="hibernate.cache.provider_class">org.hibernate.cache.TreeCacheProvider</property-->
      <property name="hibernate.cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property>
      <property name="hibernate.cache.region_prefix">hibernate.test</property>
      <!--property name="connection.datasource">java:/OracleDS</property-->
      <property name="connection.datasource">OracleDS</property>
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</property>
        <property name="hibernate.transaction.flush_before_completion">true</property>
        <property name="hibernate.connection.release_mode">auto</property>
        <property name="hibernate.transaction.auto_close_session">true</property>
        <property name="hibernate.jdbc.batch_versioned_data">true</property>
        <property name="hibernate.max_fetch_depth">1</property>
        <property name="hibernate.proxool.pool_alias">pool1</property>
        <property name="hibernate.jdbc.use_streams_for_binary">true</property>
        <property name="hibernate.query.substitutions">true 1, false 0, yes 'Y', no 'N'</property>
      <property name="hibernate.show_sql">true</property>
       
        <!-- mapping files -->
        <mapping resource="package/Pojo.hbm.xml"/>
        <...>
        <...>

    </session-factory>
</hibernate-configuration>

private void beginUserTransaction(){
        try {
            context.getUserTransaction().begin();
        } catch (NotSupportedException e) {
            throw new EJBException("Begin failed: " + e.getMessage());
        } catch (SystemException e) {
            throw new EJBException("Begin failed: " + e.getMessage());
        }
    }