Implementation of a prototype superdatabase

The Harmony heterogeneous database system with superdatabase architecture for heterogeneous transaction processing has been developed. The authors report on the implementation experience of the Harmony prototype, including the Supernova, an instance of superdatabase and three different component databases. The Supernova glues the system together. It distributes the global supertransaction to the component databases, logs the supertransaction for recovery, and validates the global serialization of the component transactions when they complete. Supernova has two important parts: The first maintains global concurrency control; the second is the distributed commit. The key problem in heterogeneous commit is the translation between different commit protocols. Supernova maintains a table of procedures that implements the commit process for each type of commit protocol. The actual commit protocol is table driven to allow easy addition of new protocols. Supernova/Ultrix currently integrates three different component databases: a modified version of university INGRES running on SUNOS, a CAMELOT server running on the MACH operating system (on a Microvax), and the Nova relational database manager