Of course if I had read the damn question I would have seen that the
question was about redo not undo. My apologies.
--
Niall Litchfield
Oracle DBA
Audit Commission UK
*****************************************
Please include version and platform
and SQL where applicable
It makes life easier and increases the
likelihood of a good answer
******************************************
"Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in message
news:3e2d1b7e$0$234$ed9e5944_at_reading.news.pipex.net...
> "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> news:sg6X9.29286$jM5.75377_at_newsfeeds.bigpond.com...
> > > On a related note, plz help me understand something that I've been
> > > meaning to figure out but since I have your ear (okay, eyes really!)
> > > I'll run it by ya .. Oracle is tracking the 'select for update' in the
> > > data block (INIT TRANS right?). Is that information actually flushed
> > > to the redo log or are INIT TRANS in-memory buckets set aside to track
> > > the select for updates?
> >
> > Damn good question. Let me slightly re-phrase it this way: does a
'select
> > for update' generate redo?
> >
> > My best guess is that no it doesn't, since after an instance recovery
you
> > would not expect certain rows to be locked. But, how to prove this? As I
> > say, good question, and a test will be forthcoming.... tomorrow.
>
> I think that this proves that it does
>
> Session 1
> select * from tab1 for update;
> <snip results>
> 29544 rows selected.
>
> Session 2
> SQL> select START_UBAFIL, START_UBABLK
> 2 , USED_UBLK ,used_urec from v$transaction;
>
> START_UBAFIL START_UBABLK USED_UBLK USED_UREC
> ------------ ------------ ---------- ----------
> 2 6478 241 29544
>
>
> No other user sessions on the db, and you have the same number of used
undo
> records as you do rows my transaction is interested in.
>
> Niall Litchfield
> Oracle DBA
> Audit Commission UK
> *****************************************
> Please include version and platform
> and SQL where applicable
> It makes life easier and increases the
> likelihood of a good answer
>
> ******************************************
>
>
Received on Tue Jan 21 2003 - 04:34:04 CST
