DDM can be used to hide or obfuscate sensitive data, by controlling how the data appears in the output of database queries. It is implemented within the database itself, so the logic is centralized and always applies when the sensitive data is queried. Best of all, it is incredibly simple to configure DDM rules on sensitive fields, which can be done on an existing database without affecting database operations or requiring changes in application code.
This looks like a nice way of getting some data masking on the cheap. It also looks like there are a couple of built-in functions for defining data types, as well as the UNMASK permission so that you don’t need to modify application code to call some type of unmasking function.