topic Limiting an SMP AlphaServer to one CPU in Operating System - OpenVMS

Limiting an SMP AlphaServer to one CPU

John F Harvey — Wed, 03 Aug 2005 21:41:05 GMT

I have a customer who wants to be able to limit his DS25 dual cpu servers to only one processor when a legacy application is run. (It will always be running, just on one node of the cluster at a time, because of the way it manipulates memory, it canot run in an SMP environment) Is there a sysgen parameter that can be set to limit the system to one, cpu, but allow the second cpu to be booted, if the first one fails? If the smp license is not installed, will the system boot with only one cpu, and also reboot to the second cpu, if the first one fails?)

Re: Limiting an SMP AlphaServer to one CPU

David B Sneddon — Wed, 03 Aug 2005 22:15:56 GMT

John,

You can put a STOP/CPU 1 command somewhere in your
startup procedures to disable the second CPU.
I don't think you can boot from other than the primary
CPU (CPU 0) and if the primary CPU dies, your system
dies. I am not aware of any SYSGEN parameters that
control this.

Dave

Re: Limiting an SMP AlphaServer to one CPU

Andy Bustamante — Wed, 03 Aug 2005 23:04:29 GMT

In addition on application end you can

START /CPU 1

to restore the full capabilities. If you remove SMP license the system will attach an OpenVMS addl-user 100 units and enable the second CPU. You'll also get a message to operator's log.

Re: Limiting an SMP AlphaServer to one CPU

Thomas Ritter — Wed, 03 Aug 2005 23:59:53 GMT

If you are running vms 7.3-2 you can restrict the application to just one cpu.

$ set proc "''process_name'" /AFFINITY/SET=0/permanent

Re: Limiting an SMP AlphaServer to one CPU

Volker Halle — Thu, 04 Aug 2005 00:49:37 GMT

John,

the SMP_CPUS system parameter (a bit-mask) can be used to prevent ANY secondary CPUs from booting. Setting SMP_CPUS to 0 will nevertheless allow the primary CPU to boot.

See $ MC SYSGEN HELP SYS_P SMP_CPUS

Volker.