By concurrent access I mean two or more programs writing to the file virtually at the same time.

BerkeleyDB knows how to lock and unlock the database so that only one program modifies the database at one time and the file doesn't get corrupted. When BerkeleyDB manages the writing, I don't need to worry about this in my programs - and file locking is easy to get wrong. The only thing I have to worry about is when two programs modify the same value at the same time, but that's something I have to think about anyway.