Message: Configured database connection is persistent. Aborting

I had the same issue, and found that it was just a matter of changing a setting:

Modify your database.php config file and turn 'pconnect' to false. As part of the CI 3 Framework, it would be part of this array:

$db['default'] = array(
    'pconnect' => FALSE // This value
);

Or if your config file looks more like the CI 2 version:

$db['default']['pconnect'] = FALSE;

A bit of searching seems to suggest that the database doesn't like a persistent connection, possible because of security reasons.

Disable caching in database.php file, define caching folder in database.php by

'cachedir' => APPPATH.'cache/db/',

setting and only use

$this->db->cache_on(); 

command where you want your database query being cached.

Don't forget to use

$this->db->cache_off();

after select queries for unwanted cached results.

It seems like codeigniter 3.0 doesn't support sessions using database, when persistent is enabled. form: http://www.codeigniter.com/user_guide/libraries/sessions.html?highlight=session#session-preferences

However, there are some conditions that must be met:

Only your default database connection (or the one that you access as $this->db from your controllers) can be used. You must have the Query Builder enabled. You can NOT use a persistent connection. You can NOT use a connection with the cache_on setting enabled.

You need to ensure that FALSE goes out without quotes.If you use 'FALSE', the database driver will take that as a true boolean. The system expects you to use FALSE directly, without quotes. So, unset pconnect instead of using 'FALSE' in order to default to FALSE, or use FALSE as a value if you like to keep things ordered :)

 * Persistent connection flag
 *
 * @var bool
 */
public $pconnect        = FALSE;