What are user-defined data types?
User-defined data types (UDTs) are data storage objects that a programmer defines to meet the needs of the application. Because they are defined by the programmer, UDTs are read by the database management system (DBMS), then stored in the database using a data type that is native to the DBMS.
ArcSDE geodatabases use several different UDTs. Some were defined by ESRI, others were defined by companies or organizations outside of ESRI. All of the UDTs utilized by ArcSDE geodatabases store spatial data, either vector or raster. Supported UDTs are as follows:
Microsoft SQL Server Geometry
Microsoft SQL Server Geography