Oracle GoldenGate Limitations and Restrictions

Oracle GoldenGate supports two types of capture:

Classic Capture
Integrated Capture

Classic Capture
Oracle GoldenGate continues to support the existing Capture module, now referred to as Classic
Capture, which directly accesses the database redo logs looking for DML changes to capture for
distribution.
It is possible to capture from redo logs stored inside of ASM. Adjusting the read
size can improve Extract performance. In this mode, Extract can be integrated
with Oracle RMAN to manage log retention.


Excellent Post by another DBA - Credit goes to him.
http://sandeepnandhadba.blogspot.com/2014/12/oracle-golden-gate-12-bidirectional.html