You need to ensure that the database users should be able to use the various flashback query features in order to go back in time by four hours. What should you do? (Choose two.)
issue ALTER DATABASE FLASHBACK ON; command
set the RETENTION GUARANTEE clause for the undo tablespace
Flashback Table, Flashback Query, Flashback Transaction Query and Flashback Version Query all rely on undo data, records of the effects of each update to an Oracle database and values overwritten in the update.
Creating a guaranteed restore point at a particular SCN enforces the requirement that you can perform a Flashback Database operation to return your database to its state at that SCN, even if flashback logging is not enabled for your database.
REF.: Backup and Recovery Basics – p1-12 and 5-4