Thanks MAK and Skhanal for your help.

Actually, the log could be less than 10mb. After kill a process which was in 'sleep' mode for 10 hours, I was able to shrink the database log to only 2 mb.
The issue is at that time, there is no 'running' process at all while erroring on 'in use' with dbcc shrinkdatabase. There is no application service on that machine. ODBC is the only connection from application to it.

-D