Dataguard => 12cR2 New Feature "Multiple Instance Redo Apply"

Starting in Oracle 12.2, we can run Redo Apply all or on some standby instances.
With this concept of multiple instance redo apply (MIRA), Redo Apply performance can scale as wide as the target RAC configuration allows.

This feature is crucial for Exadata and RAC customers with demanding high workloads on the primary database. For Active Data Guard customers, they can have real-time access to the data being churned on the primary database.

The ALTER DATABASE RECOVER MANAGED STANDBY DATABASE command, now accepts new INSTANCES [ ALL | integer] clause to start Redo Apply on multiple instances. The ALL option, starts redo apply on all the RAC standby instances that are in open or mount mode. All the instances must be in the same mounted or open mode; one instance cannot be in open mode (Active Data Guard or read-only mode) while others are in mounted mode. The integer option, specifies the number of RAC standby instances that will perform redo apply. We cannot specify which RAC instance(s) will perform the redo apply.

Starting redo apply on multiple instances has the following restrictions:
• In-Memory column store is not supported.
• Block Change tracking (BCT) is not supported.

With multi-node MRP, redo apply performance is now directly correlated to network bandwidth and latency between the primary and standby database environments