Re: DB2 Symmetric Multiprocessing (SMP)

On 17-Apr-2015 16:38 -0500, Roberto José Etcheverry Romero wrote:

On Thu, Apr 16, 2015 at 1:07 PM, Steinmetz, Paul wrote:

<<SNIP>> I remember that had an issue.

CPYFRMIMPF submits multiple jobs if DB2 Symmetric Multiprocessing
is enabled.

When you configure an LPAR you set 2 values, Total processing units
and Virtual processors, as far as I understood it if you set 2
virtual processors with 1.0 proc units you presented 2 cores with
0.5 power each to the OS which enabled you to use multithread albeit
at a lower single threaded performance. In that case, couldn't you
just test SMP modifying the amount of processors?

AFaIK the DB2 SMP knows nothing about the underlying physical CPU, only what is virtualized, so operates according to those presented virtually. There is often a clear advantage to the SMP even in such a virtual processing environment, because the difficultly otherwise, to have pushed the utilization of that one real CPU to 100%.

FWiW: I believe there was a plan to change [correct] the Copy From Import File (CPYFRMIMPF) [aka parallel load] to operate multi-threaded instead of as separate jobs to resolve the most conspicuous problem... that adopted authority is lost in that implementation, but also that the overhead for multiple jobs is far from ideal. No idea if that was ever done. Ah! the travails of transitioning /internal tooling/ to an actual feature of the OS, without hardly any system-level design oversight and I presume also hardly any /peer/ review; likely only because of the integrated security and integrity protections, there have been no security\integrity issues that had ever been reported against the import\export even given that typically disreputable origin.