CodeIgniter without a Database?

Theoretically, there should be no reason that CI needs a database. sess_use_db=false just stops CI from storing it's session information in a database. Check that you are not autoloading the database files in config/autoload.php

You could set the database type to 'sqlite' in config/database.php if you simply want to avoid setting up mysql, but you will need to have sqlite installed.

HTH

I think you should check your $autoload['libraries'] and remove database.

You just need to remove or comment the following line from autoload.php file in config folder:

$autoload['libraries'] = array('database','session');