Mnesia is a full DBMS made for telecommunications industrial needs. It has distributed transactions, fast real time lookups, crash recovery and a logical query language. The DBMS is written in the functional language Erlang which is also the intended applications language. It already has real users developing products. 1 Introduction Mnesia is a multiuser Distributed DBMS (Database Management System) specially made for industrial telecommunications applications written in the symbolic language Erlang[AVWW95]. In telecommunications applications there are needs different from the features provided by traditional DBMS's. The applications we now see implemented in the Erlang language need a mixture of a broad range of features. The most extreme among those are: 1. fast soft real-time key-value lookup 2. complicated non-realtime queries mainly for operation and maintenance 3. distributed data due to distributed applications 4. high fault-tolerance 5. dynamic re-configuration 6. variable-...