whenever your application running on various server & also db on different server .
One Day , you had -
update Schema on One Server
update various database objects on one server...
After one year or longer,organisation realize now , we require to update the db on another server .but team don't have all changes log file .
then changes in live db is very dangerous .
DataBase comparator will help out for same. even a new team member can work on it.
it also helps in day 2 days development.