Do you want create debug-log files for <b>all</b> PHP errors, even warnings, that occur during your Zen Cart store's processing?  If you want to log all PHP errors <b>except</b> duplicate-language definitions, choose <em>IgnoreDups</em>.<br /><br /><strong>Note:</strong> Choosing 'Yes' is not suggested for a <em>live</em> store, since it will reduce performance significantly!