Lock and unlock for mutual exclusion. Automatic use of parallelism without having to program explicitly. The holy grail for distributed and parallel system designers. All system calls are served by the kernal. 3 machines with .95 probability of being up.
Redundancy improves it.
Techniques that require resources linerly in terms of the size of the system are not scalable. Systems grow with time or become obsolete. Techniques that require resources linerly in terms of the size of the system are not scalable. Client-Server Computation Model processes are either servers or clients Server processes s provides services A client process sends a request message to a server process and waits for a reply message. A server waits for request messages and responds when a request arrives.