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

Oracle Error Message

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

Reason for the Error

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.

Solution

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