This is the foundation chapter for the rest of this book. We went over the basics of what Streams can do and the background processes that make up a Streams environment. Those background processes being Capture, Propagate, and Apply. Knowing each of these processes well is crucial to implementing a robust production level Streams environment. Not knowing these background processes can cause you difficulties when setting up Streams and future problems. Instantiation was covered in this chapter to point out not only what it is but to also stress its importance in the Streams environment and its role in SCN synchronization.

Streams is also dependent on the hardware and network that it runs on. Having properly sized hardware is within a DBA's influence. The network is often beyond the DBA's control. As the network is so crucial to Streams, we included discussion on the impacts of network speed and stability on Streams performance.

We also went into what an LCR is and its function. An LCR contains the DMLs and/or DDLs that are sent from Source to Target. Not all DMLs and DDLs are supported by Streams and we showed how to quickly identify what objects are supported and those that are not (query DBA_STREAMS_UNSUPPORTED).

We began to go into the Oracle Architecture (and components needed to support Streams) and Streams Performance. Chapter 7 will cover capturing Streams performance statics because it deserves its own special place. We will go into detail about how to configure the database in Chapter 3 to support optimal performance. Finally, we focus on two new Oracle 11gR2 features: Streams Change tables and XSTREAMS.

Now that we have reviewed the components of Oracle Streams Replication, let us move on to Chapter 2 where we will explore the many, many things to consider and options available when designing your Streamed environment.