Oracle® Database 11g / 12c / 18c error codes ORA-01530: a database already mounted by the instance

ORA-01530: a database already mounted by the instance

Oracle Error Code: ORA-01530

Cause: During ALTER DATABASE MOUNT, an attempt is being made to mount a database on an instance in which a database is or has previously been mounted.

Action: If you wish to mount the database, shutdown the instance and then startup the instance and retry the operation.