|
HP OpenVMS System Manager's Manual, Volume 2:... |
Managing Special Processing Environments |
|
|
|
| |
The OpenVMS operating system supports a tightly coupled, symmetric multiprocessing (SMP) system. In a tightly coupled SMP system, all processors execute a single copy of the operating system and have equal access to all operating system code and system resources. OpenVMS SMP dynamically selects the CPU where a process will run based on process priority.
A multiprocessing system can function as an isolated entity, a node in a network, or a member of an OpenVMS Cluster environment. Multiprocessing and uniprocessing systems run the same operating system, although multiprocessing can be enabled only on selected VAX, Alpha, and I64 processors. All processors in a multiprocessing environment must be at the same hardware and firmware level to guarantee that a given processor is capable of resuming the execution thread of a process that had been executing previously on another processor in the system.
Primary and Secondary Processors
In
a multiprocessing system, one processor has the responsibility of
starting other processors in the system. The primary
processor is that processor in the system that is either
logically or physically attached to the console device. As such,
it is the processor that is the target of the console commands that
boot the multiprocessing system. In this role, only the primary
processor performs the initialization activities that define the
operating system environment and prepare memory for the entire system.
In addition, the primary processor serves as the system timekeeper,
maintaining the system time and monitoring the timer queue for the
expiration of its elements. In this sense, all processors in a multiprocessing
system that do not have these responsibilities
are known as secondary processors.
Available and Active Sets
An available set is made up of the
processors that have passed the system's power-on hardware diagnostics and
may or may not be actively involved in the system. Together, the
primary and the secondary processors comprise the multiprocessing
system's available set.
The active set is the subset of the VAX, Alpha, or I64 system's processors that have passed power-on diagnostics and are actively participating in system operations. The operating system identifies each processor in these sets by its CPU ID, a value prevalent in the syntax and displays of certain DCL and utility commands.
Processor Capabilities
The processors in a multiprocessing system offer certain capabilities
to the processes executing in the system. The following capabilities
are supported:
In addition, mechanisms exist to add and subtract other capabilities.
The Run capability affects CPU starting and stopping operations.
|
|
|
