Re: Question about Undo segments

Undo segments are just rollback segments with a new name. Therefore, what was true for rollback segments remains true for undo segments.

Therefore, it's your server process that modifies undo buffers. They get flushed to disk as dirty buffers whenever DBWn takes it into its head to do any osrt of disk writing. The redo for them is the same as it is for any modification to any buffer: the before and after image.

In short, there's nothing magic about them -and if you know how rollback blocks are dealt with, that's how undo blocks are managed, too.

Regards
HJR "Jargular" <zclai_at_yahoo.com> wrote in message news:8ae4ae9e.0204270719.22c0f769_at_posting.google.com...
> Hi,
>
> Does anybody know what is the process that writes to the Undo
> segments? under what condition the Undo buffers are flushed into Undo
> segments? how are the changes in Undo buffers recorded in the online
> Redologs? I seached Oracle9i documentation, it seems that they are not
> detailed in the docs. Anyone can help?
>
> really appreciated.
>
> Jargular
> zclai_at_yahoo.com
Received on Sat Apr 27 2002 - 18:40:38 CDT