My config

$config['sess_driver']= 'database';
$config['sess_cookie_name']= 'cisession';
$config['sess_expiration']= 7200;
$config['sess_save_path']= 'ci_session';
$config['sess_match_ip']= TRUE;
$config['sess_time_to_update']= 0;
$config['sess_regenerate_destroy']= FALSE;
$config['sess_use_database']= TRUE;
$config['sess_expire_on_close']= FALSE;
$config['sess_table_name']= 'ci_session';
$config['sess_match_useragent']=FALSE;

dashbord code

<?php

if (isset($_SESSION['uid']))
{
$uid = $this->session->userdata('uid');
//print_r($userdata);
}
else {
header("Location: admin");
}

?>

controller

public function login()
    {
        $email=$this->input->post('useremail');
        $pass=$this->input->post('password');
         $check=$this->modal->check_login($email,$pass);
         if(count($check)>0){

            $uid=$check[0]->id;
            $this->session->set_userdata('uid',$uid);
            echo 1; // redirect to dashboard 
        }

Using plesk server