The original data file can be replaced by another data file.
The data file format in a new datafile however remains the same.
The schema description section in a new data file can change.
Once line 6 has executed, the client has a reference to an instance of MyServer. If ever the client releases that reference (explicitly sets the variable server to null, or exits, or crashes) then Unreferenced will be called the next time the distributed garbage collector runs following the lease expiring.