Re: Rollback segment question

Tony Adolph wrote:

> So whats the best way to avoid the problem?

Well, here's a blurb I posted previously to comp.databases.oracle.server about ORA-1555.

http://www.deja.com/getdoc.xp?AN=402881062

> > > You have missed using the following comand before you run the
> query/report:
> > >
> > > SQL> alter session set transaction read only; -- this will mark the
> select
> > > has a transaction
> > > SQL> ... long running query ...
> > > SQL> commit; -- This will free out the space reserved in the
> rollback space
> >
> > That will not prevent ORA-1555. The ability to obtain a consistent
> read of a
> > data block depends on rebuilding a block the way it looked when a
> query
> > started, based on rollback entries throughout many different rollback
> segments,
> > from other, already committed and gone transactions that were
> performed in
> > other sessions since the user's query was started. It has nothing to
> do with
> > declaring a rollback segment for the session doing the query.
> >
> > Setting a transaction READ ONLY actually sets the base SCN to which
> all reads
> > must be consistent, increasing the likelihood of ORA-1555.
Received on Wed Oct 13 1999 - 16:25:48 CDT