Which three are always benefits of using a logical standby database? 

Answer options:

A. It can be used for database rolling release upgrades.
B. It can be used to replicate a single pluggable database (PDB) in a multitenant container database.
C. It can be used as an updatable database for Real Application testing and then converted back to a standby database without affecting the updates.
D. It can be used for reporting workloads requiring additional indexes or materialized views or both.
E. It provides a disaster-recovery solution with switchover and failover options that can recover any data updated on the primary database.
F. It can be used for testing patches without affecting the primary database.

CDF

C: A logical standby database can be used to test new software releases and some kinds of applications on a complete and accurate copy of the primary`s data. It can host other applications and additional schemas while protecting data replicated from the primary against local changes. D: A logical standby database is open read/write while changes on the primary are being replicated. Consequently, a logical standby database can simultaneously be used to meet many other business requirements, for example it can run reporting workloads that would problematical for the primary`s throughput. F: Logical standby can be used to greatly reduce downtime associated with applying patchsets and new software releases. A logical standby can be upgraded to the new release and then switched over to become the active primary. This allows full availability while the old primary is converted to a logical standby and the patchset is applied. References: https://docs.oracle.com/cd/E11882_01/server.112/e41134/standby.htm#SBYDB00103