Executed as user: DOMAIN\svc_SQLService. The transaction log for database ‘dbname’ is full due to ‘LOG_BACKUP’. [SQLSTATE 42000] (Error 9002) BACKUP DATABASE is terminating abnormally. [SQLSTATE 42000] (Error 3013). The step failed.
You may get an error when you want to get a backup. In fact, the error message tells you what the error is. The main problem is that your Transaction Log file is full.
Possible scenario is that the Recovery Model of your database is FULL. There is a Transaction that has a very long or expired transaction or the space inside the Transaction Log file is full and the automatic growth of the Transaction Log file is closed or the disk is full.
In such a case, if you do not get a Transaction Log backup on a regular basis and you do not have Log Shipping, then you may consider converting the Recovery Model of the database to SIMPLE. Or you can take transaction log backups more frequently and keep the transaction log file size smaller.
If the disk with your Transaction Log file is full, then simply turning the Recovery Model to SIMPLE may not save you; in this case you may want to consider creating another Transaction Log file on another available disk.
You may want to read the following articles about the transaction log file and database recovery models.