And did you turn on debugging and get any more info?
Sometimes, locations of config files dependent upon operating system and how one is hosted.
If linux server (RH Family) and typical mysqldb server install on same host as the code, then the config file for mysqld is in /etc/my.cnf.
The settings for php are typically in /etc/php.ini ... but, check your server PHP info link for exact location of the php.ini your server is using.
You might need to install mysqltuner (Google for that) as it is a tool for tweaking DB server settings.
'spirit of sharing', Ken