e tools that enforce data integrity rules, such as the rule that
no employee can have a negative salary.  These data management services
are not common to all systems, however. Concurrency, recovery, and
transactions are the data management services that most database vendors
support.</p>
        <p>Deciding what kind of database to use means understanding the data
access and data management services that your application needs.  Berkeley DB
is an embedded database that supports fairly simple data access wi