The exits for CA 1 in general would not need to be reassembled when going to a new release of the operating system. Any exit that actually links into an IBM library, such as SYS1.LINKLIB or SYS1.LPALIB would need to be installed into the new SMP libraries for z/OS 2.1. This would include the exits for the IBM ATL/VTS devices(CTSJUCBN, CTSJUCBR, CTSJUCBX), the failsafe usermod (CTSJUSAF), and the 3480 message display exit (CTSJUMSG).