On Tue, 04 Dec 2001 03:03:43 -0500, Howard J. Rogers wrote:
> That command will only work if OPTIMAL has been set (and if OPTIMAL *has*
> been set, it's a bit unlikely he'd need to manually shrink them in the
> first place), otherwise you have to specify a size to shrink *to*.
And having "OPTIMAL" set means that your rollback segments will be shrunk
from time to time. That means that there are transactions which will
extend rollback segments beyond optimal and that SMON will shrink them
back. Now that means that some lucky transactions will have to deal with
the extents allocation in addition to the normal rollback space allocation
and on the periodical basis. This is the introduction of a lottery system
which will make some transactions 10 times slower then the other. If you
are lucky, you will have some "snapshot too old" beauties to worry about.
What I am trying to say is: do not set the OPTIMA parameter. Let you
rollbsck segments be fruitful and multiply because they're doing so for a
reason.
--
Mladen Gogala
Received on Tue Dec 04 2001 - 07:19:24 CST
