ROW GETTING LOCKED

I HAVE A PROBLEM AS FOLLOWS:
THERE ARE 2 PROCESS 'A' AND 'B' COMING TO UPDATE SAME ROW.A COMES ,UPDATES THE ROW AND IS ABOUT TO COMMIT.MEANTIME SECOND PROCESS B WHO ARRIVED LITTLE LATE IS WAITNG FOR 'A' TO RELEASE THE LOCK.BUT PROCESS 'A' HANGS JUST BEFORE COMMITING AND DOES NOT COMMIT.
I HAVE COMMIT IMMEDIATELY FOLLOWING UPDATE STATEMENT.
DATABASE IS IN NOARCHIVELOG MODE,I HAVE SET TABLE IN NOLOGGING MODE.THIS IS HAPPENING IN TEST DATABASE.v$LOCK SHOWS NO LOCKS,V4LATCH SHOWS NO LATCHES.
SOMEONE PLEASE COMMENT.

Check in V$LOCKED_OBJECT. If the row is locked , the table name will appear in this view. Ensure that row locking is enabled in the INIT.ORA file. In case of deadlock, oracle will automatically rollback one of the transactions.