Near Real-Time data capture is accomplished on most platforms using the transaction log, maintained by the database manager for the purpose of database recovery. Historically, these logs have also been the source of data for other purposes including audit or replication. Generally it is necessary and possible to configure the database manager to include additional information in the log for use by these non-recovery related activities.
All changes (Inserts, Updates and Deletes) to an Oracle Database are logged by the native Oracle Recovery Log facility. The Connect CDC (SQData) Oracle Capture agent retrieves changed data from the recovery log using the Oracle LogMiner API. While Oracle's logMiner can be configured to operate in two different modes, Connect CDC (SQData) supports raw-log capture as it presents fewer risks and provides superior recoverability. There is generally one Change Data Capture component per Oracle subsystem. Refer to Oracle documentation for further information on configuration of Oracle's LogMiner.