I'm trying to handle a planned database outage and want Drupal to show the maintenance page during that time.

• $conf['maintenance_theme'] = 'exampletheme' and a suitable $conf['_message'] are set in my sites/sitename.com/settings.php
• I have a maintenace-page--offline.tpl.php and maintenance-page.tpl.php in sites/all/themes/exampletheme/templates/
• I set $conf['maintenance_mode'] = TRUE in sites/sitename.com/settings.php

I hope that Drupal that does not have a database can still bootstrap and display the contents of maintenance-page--offline-tpl.php in this configuration, but in my testing it seems that's not the case. Should this work? Anything I should look into?