SQL*Plus in readonly mode & Performance documentation

I am looking for a way to prevent certain Oracle users from accessing the database using SQL*Plus, or perhaps they could use SQL*Plus, but in readonly mode. Is there a way to do this?

On another issue, I'm looking for documentation that encapsulates all performance related topics that should be addressed by a DBA. I find these topics to be quite "scattered" throughout the DBA Guide and wonder if anybody has a single document on performance.

Please e-mail me directly. Thank you in advance for your help.

--
Chris Little, Programmer/DBA                    University Computing Systems
                                                University of Scranton
  LITTLEC1_at_JAGUAR.UOFS.EDU                      Scranton, PA 18510