configurations=

Contains the database configuration - as is typically stored in config/database.yml - as an ActiveRecord::DatabaseConfigurations object.

For example, the following database.yml…

development:
  adapter: sqlite3
  database: storage/development.sqlite3

production:
  adapter: sqlite3
  database: storage/production.sqlite3

…would result in ActiveRecord::Base.configurations to look like this:

#<ActiveRecord::DatabaseConfigurations:0x00007fd1acbdf800 @configurations=[
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
    @name="primary", @config={adapter: "sqlite3", database: "storage/development.sqlite3"}>,
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbdea90 @env_name="production",
    @name="primary", @config={adapter: "sqlite3", database: "storage/production.sqlite3"}>
]>