Re: Differences between Undo and Rollback Segments?

I wouldn't normally consider doing this, but since Richard Foote will only stick his oar otherwise -

    The undo_retention is handled by keeping     a list of current extents with the time of the     last commit that happened in that extent;     the list is kept in the segment header block,     which reduces the number of available TT     slots. I claim this is an architectural     difference - ta-da !

BTW - do you have any indication of when Oracle will run multiple transactions into an Undo ? I haven't seen it happen yet, and the use of the retention map suggest that there is a nasty trap waiting to be engineered if it does.

--
Regards

Jonathan Lewis
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Howard J. Rogers wrote in message ...


>

>Someone is bound to mention 'undo retention'. That's not an

architectural


>change per se. It simply means that the old rule whereby the rollback

>segment's tail pointer was updated at the moment of commit is

modified so


>that it is only updated when the timeout specified by undo_retention

is


>reached. That's an artifice of kernel code, not an architectural

change to


>the rollback segments themselves, however.

>