Files are opened using the operating system disk cache in addition to the database cache.
While the operating system disk cache may improve performance, better performance is often obtained by using only the database
If the server is running on a dedicated computer, you shouldn't use the -u option, as the database cache itself is generally
more efficient. You may want to use the -u option if the server is running on a computer with several other applications (so
that a large database cache may interfere with other applications) and yet IO-intensive tasks are run intermittently on the
server (so that a large cache will improve performance).