Transaction log full due to log_backup
This error occurs because the transaction log becomes full due to LOG_BACKUP. Therefore, you can’t perform any action on this database, and In this case, 


  the SQL Server Database Engine will raise a 9002 error.


To solve this issue, you have to do the following:


Take a Full database backup.
Shrink the log file to reduce the physical file size.
Create a LOG_BACKUP.
Create a LOG_BACKUP Maintenance Plan to take backup logs frequently.



  Note: The Shrink operation effects on SQL Server Performance during executing shrink command. it also causes index fragmentation and can slow the performance of queries that search a range of the index.


So, it’s recommended before goes live you should prepare LOG_BACKUP Maintenance Plan to back up the log file frequently to avoid the shrink operation on Production.


  For more details check The transaction log for database ‘SharePoint_Config’ is full due to LOG_BACKUP 


Hope this helps you