#### Was cache automatically disabled activating maintenance mode?

Short answer: No, it **shouldn't** have.

Enabling maintenance mode shouldn't do anything to caches. It is only a mechanism to stop the bootstrapping of Magento during deployments or when you want to prevent users from getting to the website.

[Magento Dev Docs - Enable or disable maintenance mode][1]

#### What happens when activating maintenance mode?

When you activate maintenance mode, Magento will prevent the application from launching. There is a maintenance mode check in `vendor/magento/framework/App/Bootstrap.php` that calls `$this->assertMaintenance()`. It will throw an exception if maintenance mode is enabled, halting the running of the application.

This does what you would expect; Prevents users from browsing or shopping the website.

#### Pros/Cons to activating maintenance mode

##### Pros

- Prevents requests to the website from being fulfilled during Deployments / Deployment Rollbacks
- If you were performing a heavy upgrade/migration/feature deployment, keeping the site in maintenance mode would give you time to perform any manual steps before users start hitting the website
- Prevent new orders/transactions if a serious production site issue is happening and you need to firefight / troubleshoot

##### Cons

- Stops orders/transactions from coming in
- Stops users from being able to browse/interact with the website
- If activated long enough, effecting SEO crawls since all page requests will result in the maintenance mode page
- Users bouncing from the website since they are receiving maintenance mode page

#### Known Issues With Cache Automatically Getting Disabled

I'm not sure exact version numbers affected, but it is a known issue with certain versions of Magento that the caches get disabled during setup:upgrade and for whatever reason don't get re-enabled (I'll try to find the GitHub issues associated). For a few clients I've worked on this would happen during deployments and I'd have to make a note to explicitly log back into the server and enable caches after the successful deployment.

##### Links to check out related to cache disabling problem

[Magento Github Issue - cache disabled after run "composer update" command][2]

[Magento StackOverflow - Magento 2.2.x cache disabled automatically][3]

[Magento Github Pull Request - Fix to Cache Disabling Issue][4]

[Magento Github Commit - Fix to Cache Disabling Issue][5]


  [1]: https://devdocs.magento.com/guides/v2.4/install-gde/install/cli/install-cli-subcommands-maint.html
  [2]: https://github.com/magento/magento2/issues/17634
  [3]: https://magento.stackexchange.com/questions/255307/magento-2-2-x-cache-disabled-automatically
  [4]: https://github.com/magento/magento2/pull/24892
  [5]: https://github.com/magento/magento2/pull/24892/commits/af9ca675f2102aacf4003afa4d8fa779cf0b5e4e