If you get database error, access <yoursite>/xxupdate.php script at once.
MediaWiki Update

If you are using LocalSettings.php long time. Fix old style skin loader.
from old style:
require_once "$IP/skins/Modern/Modern.php";
require_once "$IP/skins/MonoBook/MonoBook.php";
require_once "$IP/skins/Vector/Vector.php";


to new style:
wfLoadSkin( 'MonoBook' );
wfLoadSkin( 'Timeless' );
wfLoadSkin( 'Vector' );
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安冨　伸浩 (マイサイト管理人)