Re: how does oracle apply rollback?

"Sybrand Bakker" <gooiditweg_at_sybrandb.demon.nl> wrote in message news:iqddiv0u62b3p2p43srrp4r2ih63abg1sm_at_4ax.com...
> On 29 Jul 2003 10:59:26 -0700, rgaffuri_at_cox.net (Ryan Gaffuri) wrote:
>
> >Connor McDonald <connor_mcdonald_at_yahoo.com> wrote in message
news:<3F266C6D.35D0_at_yahoo.com>...
> >> Ryan Gaffuri wrote:
> >> >
> >> > Does Oracle do a high level 'update' statement between the rollback
> >> > data and the table. I would think that this would not be possible
> >> > since rollback is stored differently.
> >> >
> >> > what about redo? Or what about when you do an 'online' index rebuild,
> >> > someone else updates and when complete you need to apply the changes.
> >> >
> >> > anyone know how the algorithms differ from a generic update
statement?
> >> >
> >> > I dont need to know. Im just curious.
> >>
> >> I don't think its done with anything reminiscent of SQL. If you dump
> >> out undo blocks, they typically contain just the bare bones of what is
> >> required to undo a change. eg for an insert, just the rowid; for a
> >> delete, all the "row" etc.
> >>
> >> online rebuild is somewhat different. It appears to be equivalent to a
> >> materialised view, namely, you start rebuilding and store a journal
> >> table of changes that get applied once the rebuild is complete.
> >>
> >> hth
> >> connor
> >
> >do you think on a rollback it just applies the undo directly to the
> >blocks? sort of like a direct path load? they just use C, grab what
> >they need in an array and apply the changes directly to the block?
> >
> >im assuming the undo and redo are applied the same way or am I off
> >base?
>
> 1 it does
> 2 no a direct path load is something after the HWM
> 3 It is more difficult and they have courses about it, and you will
> have to read the explanation at least 10 times, to get the idea.
> It is not THAT simple
>
>
> Sybrand Bakker, Senior Oracle DBA
>
> To reply remove -verwijderdit from my e-mail address

im assuming i have to take the course to get the documentation? Ill check metalink, but I dont remember seeing this. Received on Tue Jul 29 2003 - 15:40:44 CDT