All the backup information is stored in the MSDB database. Also, whenever a backup is taken on the database, it will be written to the error log.
While this information is useful, it could also be overwhelming, especially when you are hosting large no of databases on one instance and taking backups very frequently. In such cases, when you want to scan your error logs, to look into potential issues, it could get cumbersome with all this backup Information.
By enabling trace flag 3226, you prevent them from logging the info in the Error Log.Try this on a Test system:
Create Database Test_BKTrace
Backup database Test_BKTrace to Disk = 'E\Backup\Test_BKTrace.bak'
--check the error log, you will see information related to the backup
DBCC TRACEON(3226)
Backup database Test_BKTrace to Disk = 'E\Backup\Test_BKTrace.bak'
--check the error log, you will not find the Backup info in the error log.
DBCC TRACEOFF (3226).
However,if the backup fails, it will still log the failure message.
To enable the trace permanently on the instance, add ‘-T3226’ trace flag to the startup parameters and restart the SQL Service.
SQL Server Repository 