What is causing my Transaction log to grow
You can review events from the default trace to identify the growth events you care about:

DECLARE @path NVARCHAR(260);

SELECT 
   @path = REVERSE(SUBSTRING(REVERSE([path]), 
   CHARINDEX(CHAR(92), REVERSE([path])), 260)) + N'log.trc'
FROM    sys.traces
WHERE   is_default = 1;

SELECT 
   DatabaseName,
   [FileName],
   SPID,
   Duration,
   StartTime,
   EndTime
FROM sys.fn_trace_gettable(@path, DEFAULT)
WHERE EventClass = 93 -- log autogrow event
ORDER BY StartTime DESC;


Combined with a separate trace or extended event session you set up yourself (e.g. to capture all updates with > x duration or > y reads or writes) you can hopefully find some likely culprits around the same time from the same SPID. You won't be able to do that going back in time, of course, but you could set something up to help identify them in the future.

With that all said, your next instinct might be to fight with this process and constantly run up behind it and shrink the log file. This is not a good idea because, really, what's the point? You're going to shrink it to free up space temporarily, only so the same file can grow and fill up the space again? Please read this Q &amp; A in full:


Why Does the Transaction Log Keep Growing or Run Out of Space?