Confused about Queries and Rollback Segments!

When does a simple query acquire a rollback segment? Does it always need one or only when there are other transactions ocurring that may be updating the same rows that the query is returning? We have frequentlly run into the snapshot too old problem seemingly when the only thing running is a large query.

Thanks
Jonathan Received on Tue Nov 30 1999 - 18:01:18 CST