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Home -> Community -> Mailing Lists -> Oracle-L -> RE: redo log generation and undo_retention
undo retention does not generate more or less of anything;
it only influences how fast Oracle will reuse inactive undo segment
extents...
under 9i this is always on a "best effort" basis;
under 10g this can (optionally) be made a guarantee.
Kind regards,
Lex.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Jos
Sent: Thursday, May 13, 2004 13:07
To: oracle-l_at_freelists.org
Subject: redo log generation and undo_retention
Dear List,
I am trying to find out if setting undo_retention to non-zero value will
generate more redo log or not. I dummy up some update and insert
transactions and ran it in a 9.2 db with undo_retention=0 and
undo_retention=900 (the default), I monitored the redo size by querying
'redo size' stat in v$sysstat. And I found out that the amount of redo
generated under both undo_retention is about the same. I would have thought
that with undo_retention=non-zero value will generate more redo because of
the undo entries and these undo will be in the redo stream as well. However,
from the test result it doesn't seem to be the case. Is it my understanding
of undo is wrong or the test I did is not right?
Josh
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