Re: how does oracle apply rollback?

From: Charles Goehring <cgoehrin_at_san.rr.com>
Date: Sun, 03 Aug 2003 00:50:21 GMT
Message-ID: <h%YWa.3698$8N.322738@twister.socal.rr.com>

The Concepts manual may cover it at the high level. You probably wouldn't want to depend too heavily on it doing things any particular way because they could alway change it in another release.

Chuck

Ryan wrote:

> "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 Sat Aug 02 2003 - 19:50:21 CDT