更新Meteorjs应用程序后，MongoDB数据库会发生什么？

I am thinking about taking a deeper look into Meteor.js. I've never worked with such a framework or MongoDB before. Let's say I have a Meteor.js app running and the DB is already filled with info. Now I want to update my App. Is the Database than replaced with a new one? Because as I can see Meteor has a built in MongoDB and I have no option to run the DB and the App seperatly right?I am thinking about taking a deeper look into M