Comments on: TUNED_UNDORETENTION

by: lutz_hartmann

Thu, 14 Sep 2006 14:55:00 +0000

hope you like the papers anyway,
=;-)

by: Laurent Schneider

Fri, 08 Sep 2006 20:06:00 +0000

thanks all for the comments. apart from tinyurl, notice lutz that the link is just “apparently” truncated, that is, if you select it for copy-paste, it will be selected full.

you can also use tags on my blog !

by: yas

Fri, 08 Sep 2006 19:21:00 +0000

here it is in three parts, you must reassemble it!
Lutz, you can use tinyurl.com to shorten long urls. You can even use its bookmarklet for Firefox to shorten the url with a single click.

by: lutz_hartmann

Thu, 07 Sep 2006 02:05:00 +0000

… and here is the white paper which I like even better:
http://www.oracle.com/technology/
products/manageability/database/pdf/
ow04/1241_minhas.pdf

=;-)
LUTZ

by: lutz_hartmann

Thu, 07 Sep 2006 02:02:00 +0000

uups, sorry for the cutted link,
here it is in three parts, you must reassemble it!:

http://www.oracle.com/technology/
products/manageability/database/
pdf/ow04/1241_minhas_pres.pdf

LUTZ

by: lutz_hartmann

Thu, 07 Sep 2006 01:59:00 +0000

Hi Laurent,
I would like to point out a brilliant presentation from Oracle Open World by Munghees Minhas (principle product manager) on UNDO MANAGEMENT amoung other topics on OTN:
http://www.oracle.com/technology/products/manageability/database/pdf/ow04/1241_minhas_pres.pdf

=;-)
Lutz

by: yas

Tue, 05 Sep 2006 21:41:00 +0000

By setting UNDO_RETENTION to 0, you enable auto tuned retention

As far as I know tuned undo retention is enabled by default. Setting the undo_retention acts as a minimal threshold.

There is a difference in the tuned undo retention value between fixed size undo tablespaces and autoextend enabled tablespaces. From the 10G Release 2 Administrator’s Guide:

If the undo tablespace is
configured with the AUTOEXTEND option, undo retention tuning is slightly different. In
this case, the database tunes the undo retention period to be slightly longer than the
longest-running query on the system at that time.

Undo Retention Tuning and Alert Thresholds For a fixed size undo tablespace, the
database calculates the maximum undo retention period based on database statistics
and on the size of the undo tablespace. For optimal undo management, rather than
tuning based on 100% of the tablespace size, the database tunes the undo retention
period based on 85% of the tablespace size, or on the warning alert threshold
percentage for space used, whichever is lower. (The warning alert threshold defaults to
85%, but can be changed.) Therefore, if you set the warning alert threshold of the undo
tablespace below 85%, this may reduce the tuned length of the undo retention period.

by: Laurent Schneider

Fri, 01 Sep 2006 21:23:00 +0000

the document has been editted

by: Laurent Schneider

Thu, 31 Aug 2006 20:43:00 +0000

the document has been removed from metalink yet.

by: Laurent Schneider

Wed, 30 Aug 2006 22:34:00 +0000

I have posted feedback to metalink because the document contains errors.

One of them is :
undo_retention = 0 Which is default value in 10g

Of course the default is 900

select NAME,VALUE,ISDEFAULT
from v$parameter2
where name=’undo_retention’;

NAME VALUE ISDEFAULT
————– —– ———
undo_retention 900 TRUE