Redmine

Seriously, does anyone have a detailed "Redmine-Oracle for dummies" write-up? That doesn't assume I'm a Ruby-Rails expert or Redmine veteran or database guru? I particularly need to know-- & yes I realize Oracle's not "officially" supported-- how to resolve the following, which occurs upon attempting to log into Redmine (with database.yml set up for Oracle using oracle_enhanced-adapter):

Successful authentication for 'admin' from xxx.xxx.xx.xxx at 2016-06-23 18:23:0$ Completed 500 Internal Server Error in 37ms (ActiveRecord: 15.6ms)

OCIError (ORA-02289: sequence does not exist):
app/models/user.rb:399:in `generate_session_token'
app/controllers/application_controller.rb:82:in `start_user_session'
app/controllers/application_controller.rb:160:in `logged_user='
app/controllers/account_controller.rb:257:in `successful_authentication'
app/controllers/account_controller.rb:203:in `password_authentication'
app/controllers/account_controller.rb:189:in `authenticate_user'
app/controllers/account_controller.rb:40:in `login'
lib/redmine/sudo_mode.rb:63:in `sudo_mode'

What specific sequence is missing?