Transaction Processing in a Centralized System Due to hardware limitations, the earliest transaction processing systems were centralized. At the end of the chapter, we describe how the architectures described earlier in the chapter are implemented in this context. Some of the largest and most sophisticated transaction processing systems are on the Internet. We describe the various tasks that must be performed, show how they are mapped into modules, and explain how these modules communicate in each organization. We start with the earliest and simplest systems and then move forward in time and complexity, introducing new elements one step at a time.
In this chapter, we discuss the modular structure of these systems, taking a historical perspective. To create and maintain such a complex system, a functional decomposition into modules that perform distinct tasks is essential. Many such systems have critical performance requirements and are the foundation of vital enterprises. At the other extreme are multiuser systems in which a single transaction can access a heterogeneous set of resource managers that are distributed across a network, and in which thousands of transactions can be executing each second.
At one extreme are single-user systems accessing a local database. They must be built to respond to a wide spectrum of applications, so the demands on them vary greatly. 1 Architecture of Transaction Processing Systems Transaction processing systems are among the largest software systems in existence.
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