Oracle® Database 11g / 12c / 18c error codes ORA-12318: database (link name [string]) is already mounted

ORA-12318: database (link name [string]) is already mounted

Oracle Error Code: ORA-12318

Cause: You are attempting to mount a secondary database that has already been mounted by your instance.

Action: to mount it. To establish access, use the ALTER DATABASE OPEN command to open the database.