Re: Curiosity: single-column index on sparse data cannot be built in parallel

From: Charles Schultz <sacrophyte_at_gmail.com>
Date: Thu, 16 Jul 2015 06:35:10 -0500
Message-ID: <CAPZQniX-h17SaL+WOqCa9Ecr9j8h7hJ0NezoGMr8s5SGSGS1KA_at_mail.gmail.com>

As mentioned before, this is a Sun T5440. So even though we have 256 "virtual" cpus, the database cpu_count is set to 3 for various reasons (on our Dev box, we have so many databases we had to scale back memory consumption, so we standardized cpu_count on all non-Prod environments).

No, 100 is not very realistic, but from my point of view, I was just trying to find bottlenecks. For the most part it works beautifully. :)

BANIMP_SQL > show parameter parallel_

NAME                                 TYPE             VALUE
------------------------------------ ----------------
------------------------------
fast_start_parallel_rollback         string           LOW
parallel_adaptive_multi_user         boolean          TRUE
parallel_automatic_tuning            boolean          FALSE
parallel_degree_limit                string           CPU
parallel_degree_policy               string           MANUAL
parallel_execution_message_size      integer          16384
parallel_force_local                 boolean          FALSE
parallel_instance_group              string
parallel_io_cap_enabled              boolean          FALSE
parallel_max_servers                 integer          3600
parallel_min_percent                 integer          0
parallel_min_servers                 integer          0
parallel_min_time_threshold          string           AUTO
parallel_server                      boolean          FALSE
parallel_server_instances            integer          1
parallel_servers_target              integer          8
parallel_threads_per_cpu             integer          2
recovery_parallelism                 integer          0

On Thu, Jul 16, 2015 at 2:18 AM, Stefan Koehler <contact_at_soocs.de> wrote:

> Hi Charles,
> yes ALL means all ;-))
>
> This sounds like some kind of adaptive PX features are kicking in. Can you
> please post your "parallel_*" (show parameter parallel_) parameters?
>
> Unfortunately my leased root server is down, so i can not build up a valid
> test cases with 100 PX servers on my notebook, but just out of curiosity -
> how many CPUs do you have in your database server? Is 100 a meaningful PX
> request anyway?
>
> Thanks.
>
> Best Regards
> Stefan Koehler
>
> Freelance Oracle performance consultant and researcher
> Homepage: http://www.soocs.de
> Twitter: _at_OracleSK
>

-- 
Charles Schultz

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Received on Thu Jul 16 2015 - 13:35:10 CEST