Session store in database in cakephp 2.5.4

I am working on cakephp 2.5.4
i want to store session in database.
I have done all the steps which is list out in cookbook of cakephp.
i have create cake_sessions database.
I have configure in core.php as like
Configure::write(‘Session’, array(
‘defaults’ => ‘database’

but still now not working
i think its going something wrong way
any one can help me please…