Introduction
In this chapter, information will be
presented on the details about Down Streams capture. The nature
of the configuration will be covered as well as details on the
set up and the pros and cons of this capture method.
Down Streams
Capture
Down Streams Capture involves the execution
of the Capture process on a database other than the source
database. The archive log files from the source database are
copied to the remote database. The Capture process running on
this remote database scans and processes the archived log files
for the database changes and enqueues the Logical Change Record
(LCR) into the queue. Down Streams capture is used when the goal
is to shift the capture activity to another database, thereby
enhancing the performance of the Capture process as well as
freeing up resources at the source database.
This remote database is also known as the
Down Streams database. The queue also resides on the Down
Streams database. The archive log files are copied from the
source database, where the transactions are taking place, to the
intermediate or Down Streams database. This is accomplished by
using the log transport services, a file transfer protocol
(FTP), or by using the package dbms_ftp_transfer
mechanism.
A typical scenario of Streams data flow
involving Down Streams Capture is shown in Figure 8.1.
