I really don't understand what you are trying to achieve here.
You only need to run this command once and the SYSDATE value will remain the same until you set the parameter back to NONE. See:http://docs.oracle.com/cd/E16655_01/ser ... REFRN10062
It looks like you are just running the command loads of times, which will not affect what it does, but will burn database resources. Killing your session will have no affect on the return value of SYSDATE, because as soon as the parameter is set once, it will return the same value for ever.
I think you need to understand what initialisation parameters do before you start messing with them.