may not support concurrent shared access, and it may provide only limited security,
integrity, and recovery control.
However, modern, large multi-user DBMS products offer
all the above functions and much more. Modern systems are extremely complex pieces
of software consisting of millions of lines of code, with documentation comprising many
volumes. This is a result of having to provide software that handles requirements of a
more general nature.
Furthermore, the use of DBMS nowadays requires a system that
provides almost total reliability and 24/7 availability (24 hours a day, 7 days a week), even
in the presence of hardware or software failure. The DBMS is continually evolving and
expanding to cope with new user requirements. For example, some applications now
require the storage of graphic images, video, sound, and so on. To reach this market, the
DBMS must change. It is likely that new functionality will always be required, so that the
functionality of the DBMS will never become static.











