Re: tablespace autoextend on next size not obeyed
Date: Wed, 7 Jul 2021 11:00:54 +0300
Message-ID: <CA+riqSXyUpchd3Zrho8HUvq2tg7M3V-WKOtEP+_iOXr6enjUmw_at_mail.gmail.com>
Update:
-> looks like proactive tablespace extension is done using 64M increments,
I replicated the resize operations :
CREATE bigfile tablespace test datafile
'/u02/oradata/orcl12c/test.dbf' size 1000000k autoextend on next 1000000K ;
create table incrtest tablespace test as select * from dba_objects ;
insert into /*+ NOLOGGING APPEND parallel(4)*/ incrtest select a.* from incrtest a,incrtest;
From alert log:
Thu Jun 17 11:39:09 2021
Resize operation completed for file# 2, old size 1000000K, new size 2000000K
Thu Jun 17 11:39:09 2021
Resize operation completed for file# 2, old size 1000000K, new size 2000000K
...........................
Thu Jun 17 12:04:24 2021
Resize operation completed for file# 2, old size 22000000K, new size 22065536K
Resize operation completed for file# 2, old size 22065536K, new size 22131072K
So it looks like after some time (maybe around 30 minutes to understand a growth trend ) resize operations are done in increments of 64M.
In my particular environment my issue was that the number of such resize operations was huge (around 15K resize operations). After the latest patching activity this behavior automagically disappeared (and is not related with _max_spacebg_slaves ) . Maybe I was hitting a bug in the trend algorithm.
Thank you.
În joi, 17 iun. 2021 la 15:06, Laurentiu Oprea <laurentiu.oprea06_at_gmail.com> a scris:
> I just noticed I forgot to mention the version: 12.1.0.2
>
> În joi, 17 iun. 2021 la 14:35, Noveljic Nenad <nenad.noveljic_at_vontobel.com>
> a scris:
>
>> We observed something similar after patching. A bunch of wxxx processes
>> generated huge load to reclaim the space used by deleted LOBs.
>>
>>
>>
>> The default of _max_spacebg_slaves was huge - 1000 (?!), and we reduced
>> it to 10.
>>
>>
>>
>> Best regards,
>>
>> Nenad
>>
>>
>>
>> *From:* oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> *On
>> Behalf Of *Jonathan Lewis
>> *Sent:* Donnerstag, 17. Juni 2021 12:41
>> *To:* ORACLE-L (oracle-l_at_freelists.org) <oracle-l_at_freelists.org>
>> *Subject:* Re: tablespace autoextend on next size not obeyed
>>
>>
>>
>> Are these all bigfile tablespaces, do all the files have
>> dba_data_files.increment_by set explicitly to 10g (i.e. 1,310,720 if you're
>> using 8KB blocks).
>>
>> Is the parameter "_enable_extent_preallocation" set to 3 on production
>> and standby.
>>
>> Do the two systems have significantly different numbers of CPUs - which
>> could affect the number of Wnnn processes.
>>
>> Do you get any clues about the small allocations being handled by
>> foreground processes while the large ones are handled by Wnnn?
>>
>>
>>
>> I can't explain why you're seeing the effect, but I could imagine that
>> even a 10G (unit) allocation being shared out in units of 64MB across
>> multiple Wnnn processes thanks to some algorithm that was checking
>> concurrency, load, and CPU usage.
>>
>>
>>
>> Regards
>>
>> Jonathan Lewis
>>
>>
>>
>>
>>
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