What does it mean to freeze Ruby Gems?
NOTE: This article only applies to Deluxe and Premium hosting accounts running Hosting Configuration 2.0. Ruby on Rails is not supported for Java-enabled hosting accounts.
Freezing Ruby Gems prevents your Ruby on Rails application from automatically upgrading its Gems whenever a new version appears on the host. This allows you to control which Gems versions are run on your hosting account. The following command, run in your dev environment, unpacks the current system Gems into the vendor/rails directory: