Re: What is Parallel DML?

Howard J. Rogers wrote

>That doesn't get around the fact that at any one moment, only a single
>process can be serviced by a single CPU, regardless of capacity.

What moment? Per second? Many processes can be run on the CPU per second. Per milisecond? Per nanosecond? This argument is nonsensical.

A single CPU can service many processes simultanously. And if you look closely at the design of the new generation CPUs, even the "fact" that a CPU can only executed a single instruction in a single point in time, no longer holds true.

> >effective use, but only one of those slave process can actually have time
> >on the CPU at any given moment. And *that's* the reason my query slowed down
> >with a degree of parallelism of 2 -having to perform a context switch
> >between two processes on the one CPU is expensive.

Context switching is _not_ the issue.

> >Threads are a different game again, since there is no context switch when
> >switching between threads within the one process.

So PQs are not threads on a platform like NT? Or because PQ are threads on NT, it works on a single CPU NT machine, but not when running Linux with Oracle on that exact same machine? You are arguing in circles.

The fact is that PQ does work on a single CPU platform. Period. From a 200Mhz Pentium running Oracle 7.3 to a massive parallel cluster of single CPU Unix nodes running Oracle Parallel Server. Been there. Done that. Have the t-shirt.

>Your mileage may vary: mine never has.

Yeah, that is always a problem with closed minds that never want to understand and tweak for better mileage.

--
Billy