I was recently ask to deploy a set of changes to a production server. The changes included Drupal core and contrib module updates, as well as, updated custom theme related code.
In preparation for deployment, I placed the site into maintenance mode. Then took a database backup (using
drush sql-dump). I then pulled in the latest changes with git and updated the database (using
drush updatedb). In this case there were several updates which were executed. Finally I took the site out of maintenance mode.
The site owner was not so keen on the fact that the site was placed into maintenance mode for this procedure. He mentioned that in general they don't use maintenance mode when updating a site.
This got me wondering under what circumstances, when updating a site, should one use maintenance mode? Are there any situations when one could get away with updating a site without using maintenance mode?