session is being expired autometically

Hi,

Thank you so much for replies guys..

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = NULL;
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

$config['cookie_prefix']    = '';
$config['cookie_domain']    = '';
$config['cookie_path']        = '/';
$config['cookie_secure']    = FALSE;
$config['cookie_httponly']     = FALSE;

here is the session config and cokie config

Thanks!!