RE: UNTO TBS behavior in 9i
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <Bernard.Polarski@xxxxxxxxxxxxxx>, <daniel.fink@xxxxxxxxxxxxxx>, <adolph.tony@xxxxxxxxxx>
- Date: Thu, 25 Jan 2007 10:48:27 -0500
It is really really easy to confuse undo and redo in extended conversations
like these.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Polarski, Bernard
Sent: Thursday, January 25, 2007 9:42 AM
To: daniel.fink@xxxxxxxxxxxxxx; adolph.tony@xxxxxxxxxx
Cc: oracle-l
Subject: RE: UNTO TBS behavior in 9i
As far as I know, you will find a before image of a block in the case of the
first transaction that hits a block in a tablespace set in 'backup mode'.
Subsequent change to the block will only generate undo vectors. So there is
at least a case where you copy a full before image of a block.
However this was true for 8i. I would be surprised if it has changed since
as hot backup are rather deprecated in favor or Rman.
Bernard Polarski
Oracle DBA
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_____
From: Daniel W. Fink [mailto:daniel.fink@xxxxxxxxxxxxxx]
Sent: donderdag 25 januari 2007 14:55
To: adolph.tony@xxxxxxxxxx
Cc: oracle-l
Subject: Re: UNTO TBS behavior in 9i
UNDO (both manual in 8i/9i/10g and auto in 9i/10g) entries are not before
images of the blocks. They are actually change vectors containing only
enough information to undo the change. For example, for an insert the undo
vector is basically just the row address and a delete indicator. There are
index entries and block header entries (still not complete block images) as
well.
For more details, you can read "Automatic Undo Internals" at
http://www.optimaldba.com/papers/AutomaticUndoInternals.pdf
Regards,
Daniel Fink
NEW pop.tiscali.de wrote:
Hi all,
I think the retention setting is a red herring here. I *think* its a real
basic issue. Someone posted the suggestion to use the append hint. I
reckon this should work. You need to remember that for an insert the UNDO
is a copy of the before image and if your inserting into 30G of blocks that
have *some space* free, then all of these blocks need to be saved as UNDO.
Maybe your PCTFREE settings need looking at. Has a lot of data been
deleted - this would leave a lot of free blocks that will end up in the
UNDO. Perhaps you can rebuild the table before the insert ...or even
truncate it?
Just ideas, hope they help
Cheers
Tony
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