public class DataBaseProducer
{
    @Produces
    @PersistenceContext(unitName="default")
    @Default
    private EntityManager entityManager;

    public void dispose(@Disposes @Default EntityManager entityManager)
    {
        if(entityManager.isOpen())
        {
            entityManager.close();
        }
    }
}

public class CustomService1
{
    @Inject
    protected EntityManager entityManager;

    @Transactional
    public void update(CustomEntity1 entity)
    {
        this.entityManager.merge(entity);
    }
}

public class DataBaseProducer
{
    @Produces
    @PersistenceContext(unitName="default")
    @Default
    private EntityManager entityManager;

    @Produces
    @PersistenceContext(unitName="UserDB")
    @Users
    private EntityManager usersEntityManager;

    public void disposeDefaultDB(@Disposes @Default EntityManager entityManager)
    {
        if(entityManager.isOpen())
        {
            entityManager.close();
        }
    }

    public void disposeUserDB(@Disposes @Users EntityManager entityManager)
    {
        if(entityManager.isOpen())
        {
            entityManager.close();
        }
    }
}

public class CustomService2
{
    @Inject
    @Users
    protected EntityManager entityManager;

    @Transactional(Users.class)
    public void update(CustomEntity2 entity)
    {
        this.entityManager.merge(entity);
    }
}