Log-based CDC requires access to the data in the logs, either the active or archived ones. In general, archived logs should be kept long enough to allow the Oracle-CDC process to complete reading all the records. The length of time in which archived logs should be kept available should be calculated for each site depending on its transaction activity level and log archiving procedures.
Note that the Attunity Oracle-CDC works seamlessly with both active and archived logs, and will automatically switch between them depending on the activity level and throughput. On active and busy databases that have many transactions and changes, active logs can move to the archive quickly. The Oracle CDC Agent may still be reading the redo log when the log becomes archived and when this happens, the CDC Agent will continue to read the archived log until in finishes processing all of the changes it contains. Administrator should monitor the CDC Agent and in case of errors of missing archived logs, they should keep the logs longer.