change your application->config->config.php and set
$config[‘sess_driver’] = ‘database’;
$config[‘sess_cookie_name’] = ‘ci_session’;
$config[‘sess_expiration’] = 7200;
$config[‘sess_save_path’] = ‘ci_sessions’;
$config[‘sess_match_ip’] = FALSE;
$config[‘sess_time_to_update’] = 300;
$config[‘sess_regenerate_destroy’] = FALSE;
& Run SQL query
CREATE TABLE IF NOT EXISTS `ci_sessions` (
`id` varchar(40) NOT NULL,
`ip_address` varchar(45) NOT NULL,
`timestamp` int(10) unsigned DEFAULT 0 NOT NULL,
`data` blob NOT NULL,
PRIMARY KEY (id),
KEY `ci_sessions_timestamp` (`timestamp`)
);
