Hi,
When the log file is extremely large, then this is signal that something is wrong with your biztalk (sql) servers and you should investigate this. When time is not your friend, you could shrink the log file by using the following command. Make sure that you have stopped the host instances and the sql server agent!
sp_helpdb ’BizTalkMsgBoxDb’
ALTER DATABASE BiztalkMsgBoxDb
SET RECOVERY SIMPLE;
GO
DBCC SHRINKFILE (BiztalkMsgBoxDb_log, 1);
GO
sp_helpdb ’BizTalkMsgBoxDb’
GO
ALTER DATABASE BiztalkMsgBoxDb
SET RECOVERY FULL
GO