Global system settings, containing preferences that always apply identically to all defined users. Applications can read these
but are not allowed to write; like the "Secure" settings, these are for preferences that the user must explicitly modify through the system UI or specialized APIs for those values.
окей в вопросе есть уточнение, про
root
https://android.googlesource.com/platform/framewor...
вроде на 1018 строке нужный Вам метод