Re: newbie DBA - rollback segments

"Mark Perrault" <mperrault_at_ingdirect.com> wrote in message news:ee979b3c.0307021149.7d707a35_at_posting.google.com...
> I'm new to the oracle dba roll, so please be gentle.
>
> I load several large tables every night. My database is only about
> 20gB and is 24x7. I have 10 rollback segments of 100 mB each. I've
> noticed that the I have a rather high amount of that space getting
> used up (especially after I ran an adhoc UPDATE query on one of those
> large tables). How do I clear the RBS (beyond stopping and restarting
> the instance)? Is there a danger in having 75% or more utilization of
> those RBS's?
>
> Thanks,
> Mark

You don't clear them up. If you really are afraid you are using up too much space, or one of them is really much bigger than the others, shrink them (alter rollback segment shrink to ...)
You don't clear them up because you need to have multiple extents accomodating for multiple transactions.
Also, in dictionary managed tablespaces, extent allocation is expensive. You're going to shoot yourself in your foot also because they will grow again, when a larger transaction use the rollback segment. Once transaction commits you shrink the segment and the whole story starts over again. Configure them properly and leave them alone as much as possible.

-- 
Sybrand Bakker
Senior Oracle DBA

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