Originally posted by John Stone: I think, that this is not needed for exam.
Why not? If you're using RandomAccessFile, you will need to create that object via its constructor, so you will need to decide whether you construct RandomAccessFile with "rw", "rwd" or "rws". So if you are using RandomAccessFile this is part of the exam.
It should not matter which one you use. There is no requirement, that we should think about data being corrupted by e.g. power outage. Following this way, you may also find yourself implementing some kind of journal log to be able to recover from corrupted database and that is surely not needed.