security with storage allocation under z.OS

[Ze'ev Atlas]

Hi allIn the 1970's I probably could have done some getmain, write some code 
into that obtained memory and jump to that code.  I assume that nowadays, this 
would be impossible and there is some security model to prevent such a security 
breach.Do you know where can I find information on the mainframe security model 
under z/OS.
Ze'ev Atlas