Translations:Manual:Upgrading/91/en

This means that you should check that you have defined $DBadminuser and $DBadminpassword in your $localsettings file (in the main directory). These are the user and password needed by this script in order to access to the database. (Note: Prior to MediaWiki 1.16, these variables were located in $adminsettings. This file was removed in 1.16 and the variables were moved to LocalSettings.php.)