Where to change the "config.php" location?

[Oxygen]

Change your config.php filename, then put this as config.php:

<?
if (realpath(__FILE__) == realpath($_SERVER['SCRIPT_FILENAME'])) {
    exit('Denied.');
}

@include('yournewconfigname.php');
?>

Then simply update yournewconfigname.php with your new config name. No core edits have to occur then and your filename has been changed without hassle.