Explanation:
Database supplemental logging allows you to specify logging of primary keys, unique indexes or both. With this enabled, whenever a DML is performed, the columns involved in the primary key or unique index are always logged even if they were not involved in the DML. This only takes effect for statements which have not yet been parsed. It also invalidates all DML cursors in the cursor cache and therefore has an effect on performance until the cache is repopulated.
Incorrect Answers:
1: This statement does not create an additional copy of the database online redo log files
3: Database supplemental logging stores the primary key column values of each row involved in a DML operation in the regular, not supplemental, online redo log files.
4: It stores the primary key column values of each row involved in a DML operation in the online redo log files.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 100-110
Chapter 2: Availability Enhancements
Oracle 9i New Features, Robert Freeman, p. 68-72
Chapter 3: New Oracle9i Availability and Recoverability Features

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