Re: Huge Table Insert - take long time?

From: Woody McKay <woody.mckay_at_gmail.com>
Date: Sat, 28 Jul 2018 20:40:35 -0400
Message-ID: <CAAxONsQLVddGzSB-7La8DrMJk_wHgRdZACB0boKELESAYPqjoA_at_mail.gmail.com>



Lol... Guessing? I don't know if lower level details like exchange waits show up in explain plans, ash or awr (maybe awr and trace). I saw the exchange waits in OEM as I drilled into the session parallelism page.

The guessing comes from trying to prioritizing methods of approach and an close approaching August release date. For August, I'm taking this 12 hours insert from old to hist table out of the foreground timed release and put it in the background clean-up task (un-timed). That way I can release the main tables back to live operational status quicker.

I will setup some tests in the performance lab for these approaches and see how they benchmark. I'd like to find the best solution because I'm not sure yet if this DB will never be purging data and inefficient and un-scalable solutions will only get worse as the DB grows.

I do greatly appreciate all the great thoughts and creative approaches given.

Thanks!

On Fri, Jul 27, 2018 at 2:44 PM Mladen Gogala <gogala.mladen_at_gmail.com> wrote:

> Why? Guessing is fun. It's like fantasy football, only with other people's
> databases.
>
> On 07/27/2018 01:19 PM, Insights wrote:
>
> Stop guessing and get the awr, ash, and sql explain plan at the very
> least.
>
> Sent from my iPhone
>
> On Jul 26, 2018, at 7:58 PM, Woody McKay <woody.mckay_at_gmail.com> wrote:
>
> Ya got me thinking about the "load data by partition" idea...
>
> I wonder if instead of insert dop 16 from select dop 16, what if I have
> say 50 nonpartitioned tables (one for every partition) and dop4 insert into
> the from *_old partition () all at the same time. Then do a partition
> exchange from the 50 nonpartitioned tables to the main fully partitioned
> table? The exchange is quick since it is just a data dictionary change.
>
> This may be faster because the amount of DOP is higher. Maybe less
> exchange waits? I'm assuming that the DOP 16 can't work on all 50
> partitions all together as efficiently as loading all 50 nonpartitioned
> tables?
>
> Got me thinking...
>
>
>
>
> On Mon, Jul 23, 2018 at 8:15 PM Karthikeyan Panchanathan <
> keyantech_at_gmail.com> wrote:
>
>> What is the partition type involved here?
>>
>> One option you can load data by partition into intermediary table(with
>> new columns) and exchange. This way you can run parallel sessions for each
>> partition and before exchange new table you can build at partition level.
>>
>> You mentioned other db, have you thought about moving data from other db
>> to prod using data-pump?
>>
>> Karth
>>
>> Sent from my IPhone
>>
>> On Jul 23, 2018, at 7:52 PM, Woody McKay <woody.mckay_at_gmail.com> wrote:
>>
>> Hi gurus, I'm fishing for creative thoughts here...
>>
>> 12.1.0.2 RAC on Exadata with forced logging for standby
>>
>> There's a refactoring process: (subpartitioned tables with millions to a
>> few billions of rows)
>>
>> 1. rename the main table to main_old
>> 2. create the new_main table (no indexes or constraints at this point)
>> 3. set table prefs for concurrent incremental stats
>> 4. enable parallel dml
>> 5. insert into new_main from main_old using APPEND PARALLEL 16 (note:
>> most tables are compressed)
>> 6. create a PK or an index (as needed) on new_main
>> 7. gather table stats on new_main
>>
>> The insert in Step 5 took 9.5 hours... Total refactor process time was
>> about 13 hours.
>>
>> Is there anything you can think of to make this process any faster?
>>
>> I assume the APPEND hint isn't doing much because the DB has FORCE
>> LOGGING. Guessing alter table nologging wouldn't do much either. Can't
>> exchange from old to new since new mostly likely had columns added.
>>
>> I've mentioned using alter table if we are only adding a few columns, but
>> the production DBA's are worried about chained-rows, fragmentation,
>> possible explain plan changes, etc. I'm not sure if they are justified in
>> their thoughts.

>>
>> I've thought of doing the refactor in a diff DB (where I can truly have
>> nologging) and use transportable tablespace, but don't think that would be
>> any better.
>>
>> Any Thoughts or ideas to try?
>>
>> Thanks, as always - Woody
>>
>>
>>
>
> --
> Sincerely,
>
> WoodyMcKay
>
>
> --
> Mladen Gogala
> Database Consultant
> Tel: (347) 321-1217
>
>

-- 
Sincerely,

WoodyMcKay

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Received on Sun Jul 29 2018 - 02:40:35 CEST

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