The search order for properties is:

1. System-wide properties set programmatically (as a command-line option to the JVM when starting the application or within application code)
2. Database-wide properties
3. System-wide properties set in the derby.properties file

This means, for example, that system-wide properties set programmatically override database-wide properties and system-wide properties set in the derby.properties file, and that database-wide properties override system-wide properties set in the derby.properties file.