Re: What's in a Rollback Segment?

Answers embedded

"kopek" <matezuka_at_yahoo.com> wrote in message news:f7cb1d69.0207211206.90ce1da_at_posting.google.com...
> Hi, I would like to push this further if I could.
>
> > > - Oracle only writes the old data for the single column I updated
> > > - This data still writes an entire block to the RBS
> > > - That block is reserved thereafter for that transaction until it
> > > commits or rolls back.
> >
> >
> > That about sums it up. Mr Foote has pointed out a subtlety I didn't want
to
> > get into, which is that transactions can share the same rollback block
from
> > (I think) 8.1.6 onwards.
> >
>
> 1. It is not clear to me. So does ORACLE write "the whole data block
> that contains that particular row" to RBS? Or does ORACLE write "just
> that particular row of data to RBS which will allocate at least one
> block at the beginning of the transaction, and this RBS block can be
> used to accomodate more old data from the same transaction"?

The second option is correct.

>
> 2. The direct insert. RBS usage seems less complicated here. Just some
> undo info for the dictionary.

direct inserts are behind the HWM of the table. They will invalidate indexes.

>
> 3. The regular insert. Less undo info than update. More than direct
> insert. What is the delta in the RBS usage between regular and direct
> insert? Exactly what is written to the RBS during inserts?
>
> 4. The delete. The amount of undo generated is comparable to that of
> the update, IIRC. I would imagine ORACLE would just do a whole-sale
> copy of the old data blocks to the RBS. Right?

>
>
> - K. M.

Hth

--
Sybrand Bakker
Senior Oracle DBA

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