Finding the suitable way to store CI session

[eluser]noideawhattotypehere[/eluser]
./application/libraries/MY_Session.php

Code:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Session extends CI_Session
{

    function sess_update()
    {
       if ( !IS_AJAX )
       {
           parent::sess_update();
       }
    }

}

./application/config/constants.php

Code:

define('IS_AJAX', isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest');