Introduction

In this chapter, the basic architecture of Oracle Streams will be presented. The details will include an overview of all the resources, processes, and components that make up the data flow using Oracle Streams. Familiarity with the details of the components and the inter-relations among them yields a quick view of the overall process. The material in this chapter is the basis for Streams configuration details that will be presented in later chapters.

The basic objective of Streams is to capture, propagate, and apply database changes and user input messages. This data flow process revolves around the ‘producer and consumer’ model.

The Producer and Consumer Model

The producer is the source database system in which database changes are effected by transactional activity on the database objects. Besides the transactional input, user applications can produce the input messages which are ultimately converted into queued events for propagation. Input to the source queues may initiate from the local database system or it may come from another database, as is the case with downstream capture.  Downstream capture refers to situations where the database changes are captured in an intermediate database other than the database where the transactions are initially performed.