In the Archived Log Only (ALO) mode, Extract only reads from archived logs that are stored in a specified location. ALO mode allows Oracle GoldenGate to use production logs that are shipped over to a secondary database (such as a standby) as the data source for Oracle GoldenGate. The online logs will not be used. Oracle GoldenGate will connect to the secondary database to get metadata and other required data as needed.As an alternative, ALO mode is supported on the production system.