Critical financial market systems fault tolerant real-time client server architecture

In the early 1980´s the main requirement for electronic distribution of London Stock Exchange price information was being met by TOPIC-the Exchange´s videotex terminal system. The requirements for the new system (TOPIC²) to be implemented in July 1990 were as follows: (i) flexibility to minimise the cost of future upgrades or changes; (ii) reliability, providing high availability to users and a low level of operator intervention; (iii) high performance with sub-second response and throughput times so that updates to trading pages are reflected almost instantaneously at user terminals, while accommodating very high database update rates, (better than 33 updates per second and 333 requests per second;) (iv) expandability so that capacity and performance is limited only by the amount of hardware purchased rather than any aspect of the application or software; (v) incorporate new workstation features such as a Graphical User Interface, multiple windows, limit minders (stock watch), custom pages and scrolling tickers; (vi) maintain compatibility with the significant number of TOPIC terminals already in existence; and (vii) finally neither operational costs to the Exchange, nor the cost of the service to the user were to increase. The TOPIC ² project met its objectives in full. The Stratus based system with the broadcast and interactive link network has been used as the model for the Exchange to develop further services and it exploits the benefits of a client-server architecture at two levels-between the centre and the User Site Servers and between these and the terminals and workstations