Why is my SQL Server Transaction Log not Shrinking (or Reusing the Log file)?
Trying to figure-out why your log file for a particular database is not “naturally” shrinking is the first steps you need to take in order to diagnose and resolve a large SQL Server transaction log file.
Transaction Log files generally grow because there is something that is stopping SQL Server from reusing the already allocated space to this file, which will essentially cause the Transaction Log file to grow (as per the growth configuration settings) in order to keep the database operational. This could be caused by a natural increase in utilization for that database, or by a blockage (an active operation running too long, or waiting on mirroring to complete), so before deciding how to proceed with resolving a large Transaction Log file, it is highly recommended to figure out why did this happen.