Re: FTS, db file sequential read on undo
- From: Mathias Magnusson <mathias.magnusson@xxxxxxxxx>
- To: Vladimir Barac <vbarac@xxxxxxxxxxxx>
- Date: Mon, 13 Apr 2009 19:25:33 +0200
Hopefully someone knows this, but my thoughts were along the same lines as
what Mark said. If you do a CTAS and export from it twice, and the time
taken is the same AND you saw undo reads both times, then I think I'm at a
loss.
Mathias
On Mon, Apr 13, 2009 at 7:09 PM, Vladimir Barac <vbarac@xxxxxxxxxxxx> wrote:
> Thanks for replying, Mr. Ferguson
>
>
>
> Yes, same story – sequential reads on UNDO tablespace – happens for CTAS.
>
>
>
> Alert.log file contains lots of entries like this - Transaction recovery:
> lock conflict caught and ignored.
>
>
>
> This 10.2.0.4 RAC, standard edition.
>
>
>
> I see this for the first time in 10 years. Literally, for the first time.
>
> * *
> ------------------------------
>
> *From:* mathiasmag@xxxxxxxxx [mailto:mathiasmag@xxxxxxxxx] *On Behalf Of
> *Mathias
> Magnusson
> *Sent:* Monday, April 13, 2009 8:01 PM
> *To:* Vladimir Barac
> *Cc:* oracle-l@xxxxxxxxxxxxx
> *Subject:* Re: FTS, db file sequential read on undo
>
>
>
> Sorry. First reply and didn't watch how the "reply to" was set so it missed
> the list.
>
>
>
> Vladimir,
>
>
>
> That sounds very strange indeed. Is this a situation you see with any table
> or with just one? If you do a CTAS on dba_objects and export it, does it too
> suffer from this effect?
>
>
>
> Have you just completed a large update to this table when you run this
> analyze/export or has the table not had any recent transactions when you run
> this? Do you suffer the same problem if you run your command twice in a row
> or is it just the first invocation that shows this effect?
>
>
>
> Mathias
>
> On Mon, Apr 13, 2009 at 5:36 PM, Vladimir Barac <vbarac@xxxxxxxxxxxx>
> wrote:
>
> When accessing table for analyze or to export table, we are seeing "db file
> sequential read" wait event. V$session_wait file# is 2, that is – UNDO
> tablespace. Because of this analyze or export take forever to complete.
>
>
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