Re: UNDO: 10g-style behaviour in 18.104.22.168?
Date: Sun, 12 Apr 2009 03:12:14 -0700 (PDT)
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
> this a bit of a threat.
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:
Oracle related stuff blog: