Seaquel
SQL Server error code

SQL Server error 8309

SQL Server raises error 8309 at severity 16, which marks a problem with the query or data that you can correct.

BACKUP LOG WITH TRUNCATE_ONLY or WITH NO_LOG is deprecated. The simple recovery model should be used to automatically truncate the transaction log.
Msg8309
Severity16
Group8000–8999

Source: Database Engine events and errors