If there is no existing lock on {TAIL ~ F2}, a lock on the additional feature instance F2 is set 608 as requested, and the identifier TID1 owned by the session S1 is associated with the lock L1 and L2 on feature instances F1 and {HEAD ~ F2}, respectively 
If there is no existing lock on { TAIL ~ F2 } , a lock on the additional feature instance F2 is set 608 as requested , and the identifier TID1 owned by the session S1 is associated with the lock L1 and L2 on feature instances F1 and { HEAD ~ F2 } , respectively
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH