RAC => 12cR2 New Feature "Open Instance Read-Only Mode (Mix Mode)"

With 12cR2, there is a new cluster parameter "INSTANCE_MODE" which allows you to open an instance in read-only mode.

This parameter gives the ability your instances can be in a mix-mode.

The following information is from Oracle Docs:

• READ-WRITE instance is a regular Oracle instance.

• READ-ONLY instance is an Oracle instance that can only be opened in read-only mode.

• READ-MOSTLY instance is an Oracle instance that performs very few database writes.

These restrictions apply when setting the parameter on different Oracle Real Application Clusters (Oracle RAC) instances:

1.There must be at least one instance alive with INSTANCE_MODE set to READ-WRITE at any given time. If the only instance with INSTANCE_MODE set to READ-WRITE goes down, all other instances will be brought down by Oracle automatically.

2.An instance with INSTANCE_MODE set to READ-ONLY cannot be the first instance to open a database or any pluggable database (PDB) among all instances in an Oracle RAC cluster.

3.Oracle does not support co-existence of an instance with INSTANCE_MODE set to READ-ONLY and an instance with INSTANCE_MODEset to READ-MOSTLY in the same Oracle RAC cluster.

Demo: