Ruby on Rails
HowtoSwitchBetweenMultipleDevelopmentDatabases

If you want to switch between two databases during development, set up the database.yml like

this:

ibmdb2_development: &ibmdb2_development
  adapter: ibm_db2
  database: rpets_d
  username: user
  schema: schema
  password: password
  host: localhost
  port: 50000
  
mysql_development: &mysql_development
  adapter: mysql
  database: rpetstore_development
  username: user
  password: password
  socket: /tmp/mysql.sock

development:

  <<:  *ibmdb2_development

Then, just change last line to select which one to use.