psradm, offline, online - Stops and starts processors in a multiproces‐
/usr/sbin/psradm -f [-v] [[-a] [processor_id...]]
/usr/sbin/psradm -n [-v] [[-a] [processor_id...]]
/usr/sbin/online [-v] [processor_id...]
/usr/sbin/offline [-v] [processor_id...]
The following options apply only to the psradm command: Specifies that
all the processors except the master processor be put off line or on
line. Puts the specified processor off line. Puts the specified pro‐
cessor on line.
The following option applies to all forms of the command: Displays a
message about the status of the operation performed on each processor.
On a multiprocessor system, the psradm command puts one or more proces‐
sors off line (stops a processor) or on line (starts a processor).
The processor_id variable specifies an integer that uniquely identifies
a processor. Use the psrinfo command to display processor identifica‐
The offline command puts one or more processors off line (stops a pro‐
cessor). If no processors are specified, all processors that are on
line are stopped except the master processor.
The online command puts one or more processors on line (starts a pro‐
cessor). If no processors are specified, all processors that are off
line are started.
You must be the root user to use this command.
The /var/adm/wtmp file contains information about successful processor
Do not use the psradm command to disable CPUs when benchmarking perfor‐
mance, because the command does not provide an accurate reflection of
the performance of a system that actually has fewer CPUs. Accurate
performance results are obtained only when you disable the CPUs at the
SRM console command level.
On platforms that do not support primary processor reassignment, you
cannot use the off line command options to stop the boot processor in a
AlphaServer GS80/GS160/GS320 Series
Each quad building block (QBB) on the AlphaServer GS80/GS160/GS320
series assigns one processor to take interrupts for that QBB. If you
attempt to take this processor off line, the following error is dis‐
played: offline: processor N: Invalid argument
An interrupt-handling processor has an identifier number (N) that is
evenly divisible by 4. At present, there is no method of migrating
interrupts to another processor, therefore, you cannot take this pro‐
cessor off line.
AlphaServer ES47/ES80/GS1280 Series
Each CPU on the AlphaServer ES47/ES80/GS1280 series has the capacity to
handle I/O interrupts from either a locally attached I/O adapter or
from another CPU that has been offlined. However, each CPU is limited
to handling the I/O interrupts of two CPUs total, including its own
local I/O. Therefore, on a system with X I/O hoses, the largest number
of CPUs that can be offline at any one time is (X/2). Attempts to off‐
line more CPUs will result in the following error message from psradm:
offline: processor N: Invalid argument
There is currently no command to tell you which CPUs are handling I/O
interrupts from which I/O adapters.
The following command puts processors 2 and 3 off line: # psradm-f 2 3
The following command puts all the processors on line: # psradm-n-a
The following command puts all processors on line: # online -v
Commands: pset_info(1), psrinfo(1)