Re: question about automatic undo management

Oh well, that wasn't my experience last night. 10 undo segments created at startup, in an 8GB undo tablespace. 10 transactions each allocated to a separate segment, The 11th transaction caused a new segment to be created. The twelfth was shared. The 13th created a new segment; the 14th was shared.

I didn't pursue it much further, but now perhaps I will.

Regards
HJR "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:b0onsb$21e$1$8302bc10_at_news.demon.co.uk...
>
> I've tried to stress a 9.2.0.2 system which large
> numbers of transactions, but at present I've only
> managed to get transactions sharing an undo
> segment when it is no longer possible to create
> a new segment in the tablespace.
>
> --
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
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> Howard J. Rogers wrote in message
> <_VQX9.31337$jM5.80372_at_newsfeeds.bigpond.com>...
> >
> >Incidentally, do you know any details about the modified allocation
> policy
> >that automatic undo uses for transactions? Allegedly, it goes
> something
> >like 'assign each transaction to its own segment, until you reach a
> point
> >where you feel it appropriate to start sharing existing ones'...
> though a
> >bit of testing this end (in an 8GB undo tablespace, so plenty of room
> for
> >growth!) has indicated times when transactions 1 to 10 are assigned
> to their
> >own pre-existing segments, transaction 11 shares an existing segment,
> and
> >transaction 12 causes a new segment to be created. Transaction 13
> then
> >started sharing again. So it's rather more complicated than Oracle
> are
> >letting on!
> >
>
>
>
Received on Thu Jan 23 2003 - 13:11:41 CST