In mainframe computers many mission critical systems use Transaction Processing (TP) environment. At the core of a TP system, there is TP monitor software. In a TP system all the terminals (VDU—Visual Display Terminal, POS—Point of Sale Terminal, Printers etc.) are terminal resources (objects). There are different processing tasks, which process different transactions or messages; these are processing resources (objects). Finally there are database resources. A TP monitor manages terminal resources, database objects and coordinates with the user to pick up the right processing task to service business transactions. The TP monitor manages all these objects and connects them through policies and rules. A TP monitor also provides functions such as queuing, application execution, database staging, and journalism. When the world moved from large expensive centralized mainframes to economic distributed systems, technology moved towards two-tier conventional client/server architecture. With growth in cheaper computing power and penetration of Internet-based networked systems, technology is moving back to centralized server-based architecture. The TP monitor architecture is having a rein-carnation in the form of three-tier software architecture. In the early days of mainframes, the TP monitor and many other interfaces were proprietary. Even the networked interfaces to different terminals were vendor-specific and proprietary. The most successful early TP system was the reservation system for the American:Airlines. This was over a Uni vac computer using U100 protocol. For _IBM TV environment, which runs on OS/390 known as CI CS (Cornerstone Information Control System), the network interface was through SNA. In India when BSNI, (earlier known as DoT—Department of Telecom) launched the 197 telephone directory enquiry system in 1986, it was on IPMS (Transaction Processing Management System) running on ICE mainframe running VME operating system. The network interface was over X.25 interface.