In this chapter the basic components and
overall data and event flow within a typical Streams environment
have been presented.
The main points of this chapter include:
The basic flow at the source
database involves capture of database changes by scanning the
redo log files and converting them into LCR events. LCR events
are enqueued to a source database queue.
The Propagation process sends
the events to the specified queue in the destination database.
From a destination queue, a
typical Apply process or apply handler dequeues them and applies
the changes to the destination database objects.
Rules play an important role in
controlling the selection and transportation of the required
events. Information has also been presented on the nature of row LCRs and DDL LCRs.
In the next chapter, database replication
using the Streams methodology will be introduced. The main steps
for a typical replication flow will be examined. The information
presented will also touch upon issues such as conflict detection
and session tags.