NicC has a few good comments you should understand. As he points out, you do not want to replace the system's primary option menu, at least not until you have the new one working correctly.
- Figure out the member name of your system's primary option menu, and copy it from the system data set to your PDS, which will have the same DCB attributes as the system data set where the system's primary option menu is located.
- Insert your updates into your copy of the system's primary option menu.
- Prepare your TSO session to use your primary option table by reallocating the data set concatenation where the system's primary option menu is located with the data set containing your primary option menu before the data set containing the system's primary option menu. You will have to do this from the TSO READY prompt.
When you have done this you can start ISPF normally. In the unlikely event your primary menu is good, you can do your testing. If it is bad, the easiest recovery is to logoff and logon again, correct the problem, and repeat the previous steps.
If you do not understand this, you have no business trying to prepare your primary option menu.