Re: Rollback sizes for BIG transactions...

I don't know the total answer to this, but I have some thoughts:

The rollback segment probably must record the before image of index entries as well as data rows.

The rollback segment entry probably has overhead in the form of transaction, row and column identifiers. Null collumns must be indicated. Column length must also be indicated. Probably more overheads than I can think of.

We need some input from Oracle here.

Gene wrote:

> I've read all the info I can find regarding sizing rollback segments.
> The one item I can't find is this....
>
> How big (total size) should a rollback segment (or rather the TS holding
> the segment) be to accomodate an update of every column on every row of a
> particular table. Yeah, a bit vague. Assume the data (using VSIZE) is
> sized to be 100MB, and is all contained in the first extents sized at
> 150MB. What size rollback segment/tablespace is necessary?
>
> Intuitively, I would say 100MB, or maybe 150MB. But I tried that and
> ended up needing much much more, in fact over 400% more.
>
> thanks - gene
> gbc_at_slip.net
Received on Mon Jul 20 1998 - 11:50:48 CDT