Re: ORA-01555; does update/select sequence matter?

"John" <jbradshaw777_at_yahoo.com> wrote in message news:f2f59d82.0311111519.5c73b65_at_posting.google.com...
> Hi group,
>
> Sanity check.
> 1. There is no way to assign a rollback segment to a 'session', right?

No. Only per transaction.

> 2. It does not matter whether update or select comes first, ORA-01555
> can potentially happen, rihgt?

Not sure what the question means. 1555s generally happen because an update/insert/delete over-writes the rollback that a select elsewhere is going to need to generate it's read-consistent image of the data. If the DML happened first (and was committed), and then the select was fired off, there'd be no problem (because the select would be able to read the modified blocks directly. So the situation only really arises because one select starts, and is still running when DML happens. But it's a bit difficult to draw tidy timelines like that when you have multi-user simultaneous access.

Regards
HJR
>
> Thanks.
>
>
> John
Received on Tue Nov 11 2003 - 17:27:06 CST