Introduction

In this chapter, the configuration details of the Apply Process will be presented. In earlier chapters, the Streams clients of Capture and Propagation were examined.  The examples that started in those chapters will be extended to show the details of the Apply process.

The Apply process is an optional Oracle background process.  It dequeues Logical Change Records (LCRs) and user messages from a specific queue and then either applies each one directly or passes it as a parameter to a user-defined procedure called a handler.

The database changes are captured at the source database by the Capture process, then the Propagation process sends them to destination queue where the Apply process takes over. All of these processes fit the producer and consumer model very well.

The rules that are defined for the Apply process control the application of database table changes. Whether the changes are taken up or discarded depends on the rule that is in effect as part of the Streams Apply process. Rules are defined either automatically when the Apply process is created or they are created manually.  In the case of the manual process, the rule set will have to be associated with the Apply process.