Hi @glushkov ,
FIrst of all, there is no automated method of converting scripted fields into runtime fields, just in case you thought about it.
You can find a good & short explanation on key differences scripted vs runtime here and it will probably give you understanding about the difference in terms of user permissions.
So in short, user need to have indices privileges to set/update mappings and runtime field as part of it.
There is also a good documentation on runtime fields.
Regards, Dzmitry