What are the prerequisites for enabling Flashback Database? (Choose all that apply.)
A.
The database must be started in the MOUNT EXCLUSIVE state.
B.
The database must have multiplexed control files.
C.
The database must be opened by using a text-based parameter file instead of a server parameter file (SPFILE).
D.
The database must be in ARCHIVELOG mode.
E.
The database must be in the NOMOUNT state.
F.
The database must be opened in RESTRICTED mode.
Option A,its Deprecated now.
If your Oracle server allows multiple instances to access a single database concurrently (Oracle Parallel Server option), choose whether to mount the database exclusively or in parallel.
If you specify EXCLUSIVE (the default), then the database can only be mounted and opened by the current instance.
Not sure, if option A can be included as answer or not.
Requirements for Enabling Flashback Database
•Your database must be running in ARCHIVELOG mode, because archived logs are used in the Flashback Database operation.
•You must have a flash recovery area enabled, because flashback logs can only be stored in the flash recovery area.
•For Real Application Clusters databases, the flash recovery area must be stored in a clustered file system or in ASM.
Referred from :
http://docs.oracle.com/cd/B19306_01/backup.102/b14192/rpfbdb003.htm