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