The unit name are stored in a YAML file located in avalon/config/controlled_vocabulary.yml. The controlled vocabulary file has key value pairs that store. This file is loaded every time it is needed and is never cached. Therefore, the file can be changed without restarting Avalon.
Changing and Removing Unit Names
Each collection requires a valid unit when created or saved. Removing a unit from the unit list will not remove the unit from each collection. However, collections that have the old unit name will require selecting a new unit name before the collection can be saved.