Re: rollback segment confusion

In article <8v2n98$ucv$1_at_nnrp1.deja.com>,   mandeep2000_at_my-deja.com wrote:
> The rollback segment is not in physical memory , it is on the
> disk. ( I am new , in books I did not find it )
> for every changing row oracle moves its before image to rbs.
> does this not make query performance slow ?
> Kindly verify ?
> Mandeep
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

rollback segments are cached in the buffer cache as every other segment type is (with the exception of temporary segments). The before image is stored only if rows are *changed*, so it doesn't affect selects, more precise it affects selects only when a transaction in a different session is already going on.
And no, it doesn't make query performance slow

Hth,

--
Sybrand Bakker, Oracle DBA

All standard disclaimers apply
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