NonStop Systems Introduction

The NonStop Kernel
NonStop Systems Introduction—527825-001
6-9
Removal of Physical Boundaries
Figure 6-5 on page 6-9 shows requester-server relationships among process A, the
processor monitor, and the disk process during new process creation.
Removal of Physical Boundaries
What is unique about the message system as it has been described so far? There is
certainly nothing new about the concept of program modules passing information to
each other. That happens all the time in conventional computing environments, which
have no formal message system. In these systems, one program module usually
places the information at a specified location in memory, and another module moves
this information into its own program space.
By contrast, the NonStop message system does not assume that communicating
program modules are always running in the same processor. Nor does it assume that
memory is shared by two processors in cases where the communicating program
modules are running in different processors.
Instead, the NonStop message system is a fast, reliable mechanism for getting a
message from anywhere to anywhere in a local multiple-processor system. Because
of the message system, physical boundaries between processors make no difference.
Processes running in different processors communicate as readily as if they were in
the same processor.
The operating system can send messages anywhere in the system, because it
maintains tables that indicate where each process is executing at any given moment.
Thus, to send a message, a requester does not need to know which processor the
server is located in. All that the requester needs to supply is the name of the server
process. This name is known as a logical name or symbolic name. Using this logical
Figure 6-5. Requesters and Servers in the Operating System
Create a process
Allocate disk space
A
Disk
process
(Requester)
(Server)
(Server)
(Requester)
Processor
monitor
VST076.vsd