Re: Undo Tablespace Error

If you have AUTOEXTEND ON it is likely that the datafile had already hit the MAXSIZE.
So this would result in failure 6 in Oracle Support document " Troubleshooting ORA-30036 - Unable To Extend Undo Tablespace (Doc ID 460481.1)

Besides dba_hist_tbsp_space_usage you should also look at v$undostat (also in earlier versions dba_hist_tbsp_space_usage had bugs in reporting Tablespace Usage for Undo tablespaces)

As John says, if you have AUTOEXTEND ON, Oracle will try to keep extending Undo retention. Setting a max size for the datafiles and then setting AUTOEXTEND OFF is better.

Hemant K Chitale

On Mon, Sep 6, 2021 at 2:59 AM Lok P <loknath.73_at_gmail.com> wrote:

> Thank You John. I understand your point that with AUTOEXTENSIBLE YES
> oracle may tend to keep the expired UNDO longer to satisfy retention
> thereby increasing the UNDO tablespace to higher size. But , If we will
> talk specifically about the exact error here , isn't it true that with
> AUTOEXTENSIBLE YES, it should not have made it errored out with Ora-30036
> rather it would have thrashed/increased UNDO tablespace size by its own?
>
> Also as I see from dba_hist_tbspc_space_usage , the UNDO
> usage(tablespace_usedsize) was ~160GB which was equal to tablespace_size
> when it failed with ora-30036 , but then it increased to ~200GB after
> 4-5hrs, yet to see if somebody has increased it manually or it increased by
> itself.
>
> On Sun, Sep 5, 2021 at 2:53 AM John Piwowar <jpiwowar_at_gmail.com> wrote:
>
>> The “autoextensible” setting on your undo data files is possibly the
>> culprit here. Undo segments are a bit of a special case, and Oracle’s
>> decision-making about when to reclaim expired undo can be thrown off when
>> it thinks it has the option to extend a data file instead. It’s possible
>> that you might still need to resize your undo to accommodate recent changes
>> in your workload, but you’re better off with fixed-size undo datafiles,
>> followed by an examination of your automatic undo configuration
>> (undo_retention, etc).
>>
>> Sorry about the vagueness of the response; I’m on my phone and can’t get
>> decent references with my thumbs. :)
>>
>> On Sat, Sep 4, 2021 at 1:05 PM Lok P <loknath.73_at_gmail.com> wrote:
>>
>>> Hello Listers, In one of our 12.1 version databases, a few days back we
>>> encountered an error- "Ora-30036 Unable to extend segment by 128 in
>>> tablespace 'UNDOTBS1'" for a delete query. This failure has never happened
>>> before. And we were trying to see if we really have to increase the size of
>>> UNDO tablespace(current size is ~200GB) as it has other impacts like making
>>> long running queries run even longer before hitting ora-01555/snapshot too
>>> old etc. Or anyway we can track and fix the long transactions which might
>>> have consumed large UNDO during that time and then we can try to break that
>>> into small transactions?
>>>
>>> Another thing I notice in the dba_data_files is now showing
>>> autoextensible as YES, so how come this query errored out with
>>> Ora-30036/space issues?
>>>
>>> The USED space in dba_hist_tbspc_space_usage for this UNDO tablespace is
>>> sometimes showing completely full and sometimes it's a lot empty and i
>>> believe it's because of a circular buffer.
>>>
>>>
>>> --
>> Regards, John P. (Typed with thumbs on a mobile device. Lowered
>> expectations appreciated)
>>
>

--
http://www.freelists.org/webpage/oracle-l