systems provide some way to back up databases and to restore in the
event of a system failure that damages the database. Many commercial
systems allow <span class="emphasis"><em>hot backups</em></span>, so that users can back up
databases while they are in use. Many applications must run without
interruption, and cannot be shut down for backups.</p>
        <p>A particular database system may provide other data management services.
Some provide browsers that show database structure and contents. Some
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