资料来源 : WordNet®

database management system
     n : a software system that facilitates the creation and
         maintenance and use of an electronic database [syn: {DBMS}]

资料来源 : Free On-Line Dictionary of Computing

database management system
     
         (DBMS) A suite of programs which typically manage
        large structured sets of persistent data, offering ad hoc
        query facilities to many users.  They are widely used in
        business applications.
     
        A database management system (DBMS) can be an extremely
        complex set of software programs that controls the
        organisation, storage and retrieval of data (fields, records
        and files) in a database.  It also controls the security and
        integrity of the database.  The DBMS accepts requests for data
        from the application program and instructs the operating
        system to transfer the appropriate data.
     
        When a DBMS is used, information systems can be changed much
        more easily as the organisation's information requirements
        change.  New categories of data can be added to the database
        without disruption to the existing system.
     
        Data security prevents unauthorised users from viewing or
        updating the database.  Using passwords, users are allowed
        access to the entire database or subsets of the database,
        called subschemas (pronounced "sub-skeema").  For example, an
        employee database can contain all the data about an individual
        employee, but one group of users may be authorised to view
        only payroll data, while others are allowed access to only
        work history and medical data.
     
        The DBMS can maintain the integrity of the database by not
        allowing more than one user to update the same record at the
        same time.  The DBMS can keep duplicate records out of the
        database; for example, no two customers with the same customer
        numbers (key fields) can be entered into the database.
     
        {Query languages} and {report writers} allow users to
        interactively interrogate the database and analyse its data.
     
        If the DBMS provides a way to interactively enter and update
        the database, as well as interrogate it, this capability
        allows for managing personal databases.  However, it may not
        leave an audit trail of actions or provide the kinds of
        controls necessary in a multi-user organisation.  These
        controls are only available when a set of application programs
        are customised for each data entry and updating function.
     
        A business information system is made up of subjects
        (customers, employees, vendors, etc.) and activities (orders,
        payments, purchases, etc.).  Database design is the process of
        deciding how to organize this data into record types and how
        the record types will relate to each other.  The DBMS should
        mirror the organisation's data structure and process
        transactions efficiently.
     
        Organisations may use one kind of DBMS for daily transaction
        processing and then move the detail onto another computer that
        uses another DBMS better suited for random inquiries and
        analysis.  Overall systems design decisions are performed by
        data administrators and systems analysts.  Detailed database
        design is performed by database administrators.
     
        The three most common organisations are the {hierarchical
        database}, {network database} and {relational database}.  A
        database management system may provide one, two or all three
        methods.  Inverted lists and other methods are also used.  The
        most suitable structure depends on the application and on the
        transaction rate and the number of inquiries that will be
        made.
     
        Database machines are specially designed computers that hold
        the actual databases and run only the DBMS and related
        software.  Connected to one or more mainframes via a
        high-speed channel, database machines are used in large volume
        transaction processing environments.  Database machines have a
        large number of DBMS functions built into the hardware and
        also provide special techniques for accessing the disks
        containing the databases, such as using multiple processors
        concurrently for high-speed searches.
     
        The world of information is made up of data, text, pictures
        and voice.  Many DBMSs manage text as well as data, but very
        few manage both with equal proficiency.  Throughout the 1990s,
        as storage capacities continue to increase, DBMSs will begin
        to integrate all forms of information.  Eventually, it will be
        common for a database to handle data, text, graphics, voice
        and video with the same ease as today's systems handle data.
     
        See also: {intelligent database}.
     
        (1998-10-07)