OK so, for example if you have to change the structure of the configuration file, in a statically typed language. You have to have two representation of the data, the old one, and the new one.You have to first deserialize the data, in the old format, then convert it back to the new format, then replace the old files. The FAMF alternative, allows you just to easily use copy and paste and delete to achieve the same goal. Please keep in mind that you can just make configuration data structure that you can keep in-memory. It is just that the representation of the persisted information is spread between different files and not just one file.