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)