DB_Session not working! CI 2.0.2

[eluser]Asiansexynine[/eluser]
I am try to set $autoload['libraries'] = array('session'); in application/config/autoload.php

set config

Code:

$config['sess_cookie_name']        = 'ci_session';
$config['sess_expiration']        = 7200;
$config['sess_expire_on_close']    = TRUE;
$config['sess_encrypt_cookie']    = FALSE;
$config['sess_use_database']    = FALSE;
$config['sess_table_name']        = 'ci_sessions';
$config['sess_match_ip']        = FALSE;
$config['sess_match_useragent']    = TRUE;
$config['sess_time_to_update']    = 300;

add code to view.. to check if session work.

Code:

<?php
$session_id = $this->session->userdata('session_id');

echo 'Session ID = ' . $session_id;
?>

Now session_id were generate for my website.. but where session files store?
in phpinfo() show me that session.save_path = C:\xampp\tmp

OK.. take a look at C:\xampp\tmp but no session files generate there..
where is my session files? how to set session.save_path on CI2?