Do you have fields added to context? If so, Tableau will attempt to create a temp table for speedy provisioning of data.
No.I haven't added to context.
If your Oracle system does not allow writing -- even to a temporary table -- then you should change your user permissions on the database to revoke temp table creation privileges. This will ensure that Tableau does not attempt to utilize temporary tables as a means of accelerating queries. You may find that performance suffers when compared to a database that is not read-only, but you may have no alternative to have the functionality you desire.