Oracle Background Process

A Capture Process is an optional Oracle background process whose process name is cnnn, in which nnn is a capture process number. Capture process names include c001 through c999. A Capture process captures changes from the redo log by using the infrastructure of LogMiner.

Streams configures LogMiner automatically. The DBA can create, alter, start, stop, and drop a Capture process.  Capture process rules that control which changes a Capture process captures can be defined by the DBA. More details about Capture process maintenance will be presented in later chapters of this book.

Log Based Changes – Hot Mining or Cold Mining

From the information presented earlier, it is clear that the Streams main functionality is based on the information available from the database redo log files. Redo log files record all database changes.  Since they have a complete journal of database changes, redo log files become the perfect place to extract the database changes to propagate to the destination database.

How does this method of redo extraction differ from the queue methodology? In fact, the Streams method uses the queue mechanism in its data flow path. Staging into the queue and then subsequent propagation are the main steps.  Rather than relying on enqueued events, LogMining of the redo logs and the archived redo logs can be used when there might be a lapse in information in the queued events due to a shutdown of the Capture process.