Chapter 2. Transaction Processing Abstractions

Introduction

Transactions

Processes and Threads

Remote Procedure Call

Shared State

Scalability

Summary

2.1. Introduction

This chapter discusses five software abstractions that are used heavily in TP systems:

• Transactions

• Processes and threads

• Remote procedure calls

• Transaction context, sessions, and other techniques for managing shared state

• Caching, resource pooling, partitioning, and replication

These abstractions involve both the application programming interface and mechanisms to support it. Understanding them is fundamental to developing and engineering a TP system.

We start with the transaction abstraction, where we focus on the semantics of the programming model. We present pseudocode that illustrates how a transaction is delimited and thus establishes the relationship between a program and the TP infrastructure. This sets the stage to discuss the significant abstractions relevant to that infrastructure-processes, threads, and remote procedure call-where the focus shifts from the programming model to how the mechanisms work. Then we present the main abstractions involved in state management, which are at the core of the leading programming and deployment models used in transactional middleware. Finally, we talk about abstractions that are used to enhance the performance and scalability of TP applications: caching of state; pooling of sessions, threads, and other resources; and partitioning and replication of databases and server processes.