Introduction
In this chapter, the implementation of
Streams in a typical Real Application Clusters (RAC) environment
will be presented. With many businesses adopting RAC database
technology for their data needs, the topic of Streams in a RAC
environment will be of high importance. The differences in the
Streams configuration in a RAC environment will be highlighted.
Information will be included on the extra things that need to be
considered on account of the database environment being a RAC.
Streams in a RAC
Environment
A RAC is a single database with multiple
instances. Each instance in the RAC database environment has its
own set of redo log files. Each instance thread produces its own
set of archived log files; however, those redo log files and
archived log files are accessible to all of the instances. Redo
and archived log files reside on shared storage. Shared storage
is configured either as an approved cluster file system or
through Oracle’s Automatic Storage Management (ASM).
As shown in Figure 9.1, each of the RAC
database instances consists of the following: Instance-1 has
redo groups from 1 to 3; Instance-2 has redo groups 4 to 6; and
Instance-3 has redo groups 7 to 9. The Streams Capture process
extracts all the database changes recorded in all of the redo
log files.
Figure 9.1 Typical RAC database
environment
The Oracle10g Database release has brought
in two important enhancements:
