I'm not the most experienced here but I assume $wgReadOnly would require a TRUE/FALSE argument rather than a text string.
----- Original Message -----
I want to move my wiki to another server (and upgrade at the same time
from 1.14 to 1.16.2).
I simply need to make the old wiki readonly, while I move, upgrade and
change the redirect URL - so I placed $wgReadOnly = 'Upgrading to MediaWiki 1.16.2';
In the localsettings.php file.