Grails allows developers to store data in either an embedded or external database. Embedded databases are lightweight and require little configuration as they are linked directly to the application, while external databases like MySQL can be shared across multiple programs concurrently but require more setup. Grails supports development, test, and production environments which can be configured with different database settings in the DataSource.groovy file. Developers can run the application in each environment using specific Grails commands like 'grails run-app' for development and 'grails prod run-app' for production.

1. Grails Data
Kendrew Lau

2. Grails stores all data in database
Embedded database
No database server, a library linked to a
program for data access
Lighter, require less/no configuration
E.g., HSQLDB embedded mode
Database server
External process that manages data access
Can be shared/accessed by multiple program
concurrently
E.g., MySQL

3. Grails has 3 environments
3 configurations with possible different
database settings
development
test
production
Configured in file
grails-appconfDataSource.groovy

4. To execute in the 3 environments
Development
grails run-app
grails dev run-app
Test
grails test run-app
Production
grails prod run-app