Oracle

To create a new Rails application that uses the Oracle adapter:

$ rails -d oracle my_rails_app

Next, edit config/database.yml with the proper settings.

development:
  adapter: oracle
  username: scott
  password: tiger
  database: database_name
  timeout: 5000

For server-side database instances, there appears as of ActiveRecord 2.2.2 and possibly earlier versions, to be a problem using aliases defined in tnsnames.ora. It may be easier to define the database address more explicitly, e.g:

database: (DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(Host=<host 
  address>)(Port=<port>)))(CONNECT_DATA=(SERVICE_NAME=<service name>)))

To install a local instance of Oracle for development and possibly testing, download and run the Oracle 10g Express Edition installer as appropriate for your operating system environment.

$ gem install activerecord-oracle-adapter --source http://gems.rubyonrails.org

$ sudo gem install activerecord-oracle-adapter --source http://gems.rubyonrails.org

oracle_adapter.rb should be copied to \lib\active_record\connection_adapters within the ActiveRecord gem directory

The activerecord-oracle-adapter does not appear to be under active development at this time. An alternative adapter for Oracle is the oracle-enhanced adapter. To install the enhanced adapter do the following:

$ sudo gem install activerecord-oracle_enhanced-adapter

$ gem install ruby-oci8 -v 1.0.4

$ sudo gem install ruby-oci8 -v 1.0.4

Rails 2.3 does not work with ruby-oci8 2.0.0