Rails 3 - how do I avoid database altogether?

I'm trying to use rails 3 without any db backend, but it still insists on requiring 'sqlite3' gem when I try to access a page, and throws an error no such file to load -- sqlite3, even though no code in the application requires sqlite, except I left database.yml with its default setting for sqlite3, since removing the content raised other errors. Any idea how I could use rails without any database and avoid said errors? thanks.

(also, I'm familiar with Sinatra - just prefer rails for this project).

Rails 3:

In application.rb, remove the require 'rails/all' line and instead add these lines:

require "action_controller/railtie"
require "action_mailer/railtie"
require "active_resource/railtie"
require "rails/test_unit/railtie"
require "sprockets/railtie"

Also see Remove ActiveRecord in Rails 3 and look into the Active Model railscast

Rails 3.2.x:

You'll also need to remove/comment out this line in application.rb

config.active_record.whitelist_attributes = true

And remove/comment these two lines from development.rb

config.active_record.mass_assignment_sanitizer = :strict
config.active_record.auto_explain_threshold_in_seconds = 0.5

Rails 2.x:

In config/environment.rb add (or uncomment) the line

config.frameworks -= [ :active_record, :active_resource, :action_mailer ]

This will cause Rails not to use those frameworks. (Note the nearly-invisible -= !)

Also, in Rails 3, remove any references to active_record in

config/environments/development.rb

config/environments/test.rb and

config/environments/production.rb such as

config.active_record.mass_assignment_sanitizer = :strict
config.active_record.auto_explain_threshold_in_seconds = 0.5

as well as removing require "rails/all" and adding the require lines in comment 21 (above).

if you are not using a database (this works with Rails 3.1.1)