public boolean crearLink(String nombre, String usuario, String password, String host, String port, String serviceName) throws GlobalException, NoDataException, SQLException{ 
        
        boolean exito = false;
        try {
            conectar(user, pass,ip,port,db); 
        }
        catch(ClassNotFoundException ex)
        {
            exito = false;
        }
        ResultSet rs = null;
        PreparedStatement stmt = null;
        try{
            String query = "CREATE DATABASE LINK "+nombre+" CONNECT TO "+usuario+" IDENTIFIED BY "+password+" USING '(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = "+host+" )(PORT = "+port+" ))(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = "+serviceName+" )))'";
            stmt = conexion.prepareStatement(query); 
            System.out.println(query);
            stmt.executeQuery();
            exito = true;
        } catch (SQLException e) {
            exito = false;
            e.printStackTrace();
            throw new GlobalException("Sentencia no valida");
            
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                desconectar();
            } catch (SQLException e) {
                throw new GlobalException("Estatutos invalidos o nulos");
            }
        }

        return exito;
    }