TSQL LOCK!

         (UPDLOCK)    (HOLDLOCK)  (UPDLOCK,HOLDLOCK)  (TABLOCKX)
---------------------------------------------------------------------------
SELECT  not blocked    not blocked     not blocked         blocked
INSERT  not blocked      blocked         blocked               blocked
UPDATE    blocked         blocked         blocked               blocked
DELETE     blocked         blocked         blocked               blocked

 

http://stackoverflow.com/questions/7843733/confused-about-updlock-holdlock