Which three statements are true about snapshot standby …

Which three statements are true about snapshot standby databases?

A.
Snapshot standby databases may be used for rolling release upgrades.

B.
If datafiles grow while a database is a snapshot standby database, then they shrink when converted back to
a physical standby database.

C.
Flashback logs are used to convert a snapshot standby database back into a physical standby database.

D.
A snapshot standby database can have Real-Time Query enabled.

E.
A guaranteed restore point is created automatically when a physical standby database is converted into a
snapshot standby database.

Explanation:
C: Flashback Database is similar to conventional point-in-time recovery in its effects. It enables you to return a
database to its state at a time in the recent past. Flashback Database uses its own logging mechanism,
creating flashback logs and storing them in the fast recovery area. You can only use Flashback Database if
flashback logs are available. Flashback Database is used to convert a snapshot standby database back into a
physical standby database.
E: When we convert the physical standby database to snapshot standby database a guaranteed restore point
is created. This guaranteed restore point is used to flashback a snapshot standby database to its original state.
Incorrect Answers:
A: Oracle Database supports the installation of database software upgrades, and the application of patch sets,
in a rolling fashion—with near zero database downtime—by using Data Guard SQL Apply and logical standby
databases.

https://docs.oracle.com/cd/E11882_01/server.112/e41134/manage_ps.htm#SBYDB4803
http://satya-dba.blogspot.se/2012/06/snapshot-standby-databases-oracle.html