In this post, you’ll learn more about the Oracle ErrorORA-15168: rolling downgrade prevented by string with the details on why you receive this error and the possible solution to fix it.
Oracle Error Description
ORA-15168: rolling downgrade prevented by string
Reason for the Error ORA-15168: rolling downgrade prevented by string
One or more instances were blocking the rolling downgrade.
How to fix the Error ORA-15168: rolling downgrade prevented by string ?
You can fix this error in Oracle by following the below steps
Terminate or wait until the reported operation is complete before attempting the rolling downgrade to the cluster.