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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Undo x Rollback Segments in 9i
One issue I have observed with System-Managed Undo is that Oracle seems to be very aggressive about keeping the rollback segments the 'right' size for the keep-time.
In the one set of tests I ran, this resulted in frequent extends and shrinks of the generated rollback segment, with a resulting I/O load appearing on the datafile holding the rollback segments. The work-around was to increase the keep time to a higher value than necessary - which still resulted in extra I/O, but not such an excessive amount.
I still have to set up further test scenarios but, at first usage, it seems that system managed rollback segments MAY be a problem when used on a finely tuned system with carefully selected rollback segment sizes.
Jonathan Lewis
http://www.jlcomp.demon.co.uk
Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html
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Author: Jonathan Lewis
INET: jonathan_at_jlcomp.demon.co.uk
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