public void iniciarTransaccion() {
		try {
			if (tx != null && tx.isActive()) {
				concretarTransaccion();
			}
			// -----------------------------------------
			persistencia = SingletonConexion.getPmf().getPersistenceManager();
			// -----------------------------------------
			// setTransactionIsolation ???
			tx = persistencia.currentTransaction();
			tx.begin();
		} catch (Exception E) {
			System.out.println("Error al iniciar la transaccion: \n");
			E.printStackTrace();
		}
	}