How to shutdown an app deployed on Heroku?

I have an app on Heroku which is being used by few users. However, I notice there are some data issues which I'd like to fix and stop the app in the mean time so users don't enter anything new.

Is there a way to stop the app on Heroku rather than destroying it? I see that restart server command is there... Although I don't see anything like 'stop'.

To completely 'stop' your app you can scale the web dynos down to zero which effectively takes all your app http-processes offline.

$ heroku ps:scale web=0
Scaling web processes... done, now running 0

http://devcenter.heroku.com/articles/maintenance-mode

If you’re deploying a large migration or need to disable access to your application for some length of time, you can use Heroku’s built in maintenance mode. It will serve a static page to all visitors, while still allowing you to run rake tasks or console commands.

$ heroku maintenance:on
Maintenance mode enabled.

and later

$ heroku maintenance:off
Maintenance mode disabled.

From the Heroku Web

Dashboard => Your App Name => Resources => Pencil icon=> Flip the switch => Confirm

Go to your dashboard on heroku. Select the app. There is a dynos section. Just pull the sliders for the dynos down, (a decrease in dynos is to the left), to the number of dynos you want to be running. The slider goes to 0. Then save your changes. Boom.

According to the comment below: there is a pencil icon that needs to be clicked to accomplish this. I have not checked - but am putting it here in case it helps.