Re: parallel query and latch waits

Based on your analysis, I guess it's even better the original poster runs his query without parallel execution because PX slaves have to sleep or spin on the latches anyway, and sleep involves context switch overhead.

I wonder if we can tell each PX slave to read certain rows so two slaves won't touch each other's "assignment". At the end, the SUM(IMPRESSIONS) in the original query is done based on each slave's result.

Yong Huang
yong321_at_yahoo.com

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:<992085220.7197.0.nnrp-01.9e984b29_at_news.demon.co.uk>...
> It is the nature of parallel queries that they
> will raise the level of buffer latch contention -
> especially if they involve some sort of join
> or correlated subquery, as you are much
> more likely to get several processes (i.e. the
> PX slaves) all demanding the same set of
> buffered blocks at the same time.
Received on Sat Jun 09 2001 - 16:16:43 CDT