ORA-01138: database must either be open in this instance or not at all

Oracle error

ORA-01138: database must either be open in this instance or not at all

Cause: The requested operation can not be done when the database is mounted but not open in this instance, and another instance has the database open.

Action: Execute the operation in an open instance, open the datbase in this instance, or close the database in the other instances.

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