User-defined data types are like user-defined functions to create customized data types.

UDD Type Example

For example, CREATE DISTINCT TYPE AUDIO AS BLOB(1M);

So now the “audio” becomes a new data-type. If we talk about user defined data types, there are 2 types.

Distinct Type

In this case, the only user-defined type is customized based on an existing type

Structured Type

CREATE TYPE PERSON_DET AS (NAME CHAR(20),
AGE INT,
ADDRESS ADDRESS_T,
INSTANTIABLE
REF USING VARCAHR(13) FOR BIT DATA
MODE DB2 SQL;

The basic difference is , we can create a structure with mix of db2 existing types and UDTs.

The usage for UDTs we can see in the Banking domain.