Oracle Error ORA-15166: cluster in rolling downgrade from version [string] to [string]

Oracle Error Message

ORA-15166: cluster in rolling downgrade from version [string] to [string]

Reason for the Error

The current software version of the instance was incompatible with the rolling downgrade operation of the cluster.

Solution

The version number of new member instance must be one of the two versions involved in the rolling downgrade.