Oracle® Database 11g / 12c / 18c error codes ORA-12326: database [string] is closing immediately; no operations are permitted

ORA-12326: database [string] is closing immediately; no operations are permitted

Oracle Error Code: ORA-12326

Cause: The database you attempted to access is closing, so your operation has been terminated.

Action: Wait until the database has been reopened, or contact the database adminstrator.