Source : Free On-Line Dictionary of Computing

system catalog
     
         The {data dictionary} of a {DBMS}.  The system
        catalogue stores {meta-data} including the {schemas} of the
        {databases}.  It is a mini-database, and is usually stored
        using the DBMS itself in special {tables} called {system
        tables}.  It maybe referred to as being "on line", as it is
        active, and can be queried by users like any other table.
     
        (1999-04-27)