The tests were done using T-SQL for the database and log backups.

All databases are in 'Full Recovery' mode.

The SQL Server Log does show this entry repeatedly:

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

But I not see anything in the Maintenance plan that would indicate that the recovery modes are switched.

In addition further research has led me to run this query:

SELECT

DB_NAME(database_id), last_log_backup_lsn

FROM

sys.database_recovery_status;

This shows that the two problem databases have the last_log_backup_lsn = NULL

I gather this means the log backup chain is broken and it has be restarted.

Would the correct procedure be:

1. Stop all user activity in the database

2. Switch to the SIMPLE recovery model (breaking the log backup chain)

3. Switch to the FULL recovery model

4. Take a full database backup (thus starting a new log backup chain)

5. Start taking log backups

Thanks in advance.