<?xml version="1.0" encoding="UTF-8"?>
<persistence>
  <persistence-unit name="DB1">
  <jta-data-source>java:/MySqlDS</jta-data-source>
  <properties>
     <property name="hibernate.hbm2ddl.auto"
              value="create-drop"/>
    <property name="hibernate.dialect"
              value="org.hibernate.dialect.MySQLDialect"/> 
  </properties>
  </persistence-unit>
<persistence-unit name="DB2">
  <jta-data-source>java:/MySqlDS2</jta-data-source>
  <properties>
     <property name="hibernate.hbm2ddl.auto"
              value="create-drop"/>
    <property name="hibernate.dialect"
              value="org.hibernate.dialect.MySQLDialect"/> 
  </properties>
  </persistence-unit> 
</persistence>

@Entity
class A {
}