Managing CPU_COUNT for micro-partitioning on AIX

Hey all,

As I'm researching what I need to know about AIX for a new 10gR2 install, I'm wondering about _CPU_COUNT. We're buying an IBM 2x2 (two dual-core CPUs) JS21 blade that will be running IBM's Advanced POWER Virtualization (APV). APV is a way to virtualize resources -- let's say
"CPUs" -- for multiple OS installations on the same box, with the
ability to prioritize the virtual partitions' CPU usage. APV enables assigning a dedicated amount of CPU to individual partitions, as well as a shared amount of CPUs.

The kicker is that APV allows partial-CPU assignments. For three virtual partitions, "DEV", "BETA", and "PROD", one could assign 0.1 (yes, "one-tenth") CPUs to each of "DEV" and "BETA" and 2.0 CPUs to
"PROD", leaving the remaining 1.8 CPUs free for the shared pool of CPUs,
giving priority to "PROD". So when "PROD" needed CPU, it would take up to 3.8 CPUs. And if "DEV" or "BETA" needed more CPU and "PROD" wasn't using it, they could use up to 1.9 CPUs, depending on priority, up to the full 4.0 CPUs. That's the gist of APV as I understand it. There's more at http://www-03.ibm.com/systems/p/apv/sc.html if anyone's interested.

ANYWAY, does anyone know how Oracle would or should handle the _CPU_COUNT and the continuously variable CPU allowance? I still don't exactly how the APV Hypervisor determines what a tenth of a CPU is, but I'm thinking that _CPU_COUNT won't take decimals or fractions. I've found a possible vague reference to this in licensing at http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/FQ114190 but nothing regarding performance and init.ora parameters.

And, no, I've already refused to put "DEV" and "PROD" on the same box. I don't care if it's virtual or not. Because no one's ever had an HBA/SAN/CPU/RAM fail or not failover perfectly...

Thanks!
Rich

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