Re: UNDO: 10g-style behaviour in 9.2.0.8?

From: Randolf Geist <mahrah_at_web.de>
Date: Sun, 12 Apr 2009 03:12:14 -0700 (PDT)
Message-ID: <2136c9b5-fe13-4a32-b27c-8864f2ce0ea6_at_z19g2000vbz.googlegroups.com>

On Apr 11, 3:52 pm, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk> wrote:
> I can't recall seeing anything that says the value you set is the floor
> value -
> a reference would be useful as I've had one client run into problems with
> automatic undo retention in 10.2.0.3 where the tuned_undoretention dropped
> to a value much lower than their setting.  There particular circumstances
> made
> this a bit of a threat.

Jonathan,

it's documented behaviour in 10g automatic undo tuning that if the available space in the UNDO tablespace is restricted (autoextend off), the UNDO_RETENTION parameter is simply ignored and tuned to whatever is possible given the space available and the current workload, so it can well go below the defined UNDO_RETENTION value.

See e.g. here:

http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/logical.htm#sthref454

http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/undo.htm#ADMIN10180

Regards,
Randolf

Oracle related stuff blog:
http://oracle-randolf.blogspot.com/

SQLTools++ for Oracle (Open source Oracle GUI for Windows): http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/ Received on Sun Apr 12 2009 - 05:12:14 CDT