AST's in RAC environment

Today, I've had a little clash with Gopal (K. Gopalakrishnan), a well known oracle professional. The issue at stake was the use of the term AST.

AST, for those who don't know that is a VAX/VMS abbreviation for
"Asynchronous System Trap" and was, essentially, VMS way of executing
your code in the context of another process. Blocking AST was an AST which elevated IPL (Interrupt Priority Level) above 2, which was the interrupt priority of the system clock (VMS internals, from the time when dinosaurs were roaming the Earth and when I was teaching a course called "tuning VMS"). The term AST is used in the context of RAC.

I didn't get the answer what is AST supposed to be, the answer was that AST is "something like interrupt". Well, I am not a complete stranger to Unix and I've never seen serious people using terms like
"something like interrupt". Gopal obviously doesn't know the principles
of that implementation or what is it supposed to do. I am, therefore, forced to ask the general public: is there anybody , on the vast expanses of Usenet, who can precisely define what is AST, in the context of the Real Application Cluster? The question is: does anybody know how do these
"AST" things really work, in terms of sockets, signal, IPC and other
familiar Unix mechanisms? Original AST's were using architecture specific features of NVAX and CVAX chips.
Until now, I was making sure that any oraclite trying to look smart by mentioning AST and RAC in the same sentence in my presence takes home a memorable experience, but I do have nothing but respect for Gopal's knowledge and skills. I was dismissing the AST talk as the terminology used by the old VMS aficionados, but now I am confused. What is going on here? Metalink doesn't come up with anything when "RAC AST" is entered into the search engine. Where does this AST snake oil come from? I came accross the expression in Steve Adams internals book, but AST isn't defined there, either.

-- 
Artificial Intelligence is no match for natural stupidity.