8 uses of MAINTENANCE_MODE in Drupal 7

ajax_footer in includes/ajax.inc

Performs end-of-Ajax-request tasks.

drupal_exit in includes/common.inc

Performs end-of-request tasks.

drupal_installation_attempted in includes/bootstrap.inc

Returns TRUE if a Drupal installation is currently being attempted.

error_displayable in includes/errors.inc

Determines whether an error should be displayed.

menu_get_custom_theme in includes/menu.inc

Gets the custom theme for the current page, if there is one.

update_flush_caches in modules/update/update.module

Implements hook_flush_caches().

_drupal_bootstrap_full in includes/common.inc

_drupal_maintenance_theme in includes/theme.maintenance.inc

Sets up the theming system for maintenance page.