GSquared (10/30/2012)
sp_who2 should tell you which SPIDs are active in tempdb. Can use the Management Studio activity monitor (right-click the server name in the object explorer if you haven't use that tool before), but that can be a pain since it updates constantly.DBCC SQLPERF(LOGSPACE) should tell you how much log space is being used.
I see that ONLY 25% is being used. I did try to take with backup with truncate_only option and then shrink,still log file shows 38 gb.?