Shrink SharePoint configuration database log file

USE DatabaseName
GO                
BACKUP LOG <DatabaseName> WITH TRUNCATE_ONLY
DBCC SHRINKFILE(<TransactionLogName>, 10)

Where 10 is the size to which the log file will be shrrinked..in this case it is 10 MB

You can also do it from the SQL Management Studio

Right Click on Database --> Tasks -->Shrink –>Files—>Select “Log” option from the dropdown and then select the shrink size