How to fix the Oracle error ORA-12809: cannot set string_INSTANCES when mounted in exclusive mode?

In this post, you’ll learn more about the Oracle ErrorORA-12809: cannot set string_INSTANCES when mounted in exclusive mode with the details on why you receive this error and the possible solution to fix it.

Oracle Error Description

ORA-12809: cannot set string_INSTANCES when mounted in exclusive mode

Reason for the Error ORA-12809: cannot set string_INSTANCES when mounted in exclusive mode

An attempt was made to set SCAN_INSTANCES or CACHE_INSTANCES using the ALTER SYSTEM command while the database was mounted in exclusive mode.

How to fix the Error ORA-12809: cannot set string_INSTANCES when mounted in exclusive mode ?

You can fix this error in Oracle by following the below steps

SCAN_INSTANCES / CACHE_INSTANCES may not be set unless running Oracle Real Application Clusters mounted in CLUSTER_DATABASE mode.