Is there oracle Audit Trail as built-in functionality?
oracle
Audit Trail
Do I need to create a separate table for Audit Log to record INSERT, UPDATE and DELETE changes?
Audit Log
INSERT, UPDATE
DELETE
Yes, Oracle supports auditing. You will not need to create audit tables yourself, but you will need to configure audit parameters (i.e. which tables / users / requests for audit).
http://download.oracle.com/docs/cd/B28359_01/server.111/b28318/security.htm#i16445