<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="
        http://java.sun.com/xml/ns/persistence
        http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="Tarea2DS" transaction-type="JTA">
        <jta-data-source>java:jboss/datasources/Tarea2DS</jta-data-source>
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="create" />
            <property name="hibernate.show_sql" value="true"/>
        </properties>
    </persistence-unit>

</persistence>

<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="
        http://java.sun.com/xml/ns/persistence
        http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="Tarea2DS" transaction-type="JTA">
        <jta-data-source>java:jboss/datasources/Tarea2DS</jta-data-source>
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="hibernate.show_sql" value="true"/>
        </properties>
    </persistence-unit>

</persistence>

Update instead of dropping shema
Update instead of dropping shema
