You can use a DTD to validate XML data in an XML column or in an XML collection. The DTD validates the XML column and is used to define DAD files that are used for XML structural search and for collection composition and decomposition.
All DTDs are stored in the DTD repository, a DB2 table called DTD_REF. It has a schema name of db2xml. Each DTD in the DTD_REF table has a unique ID. The XML Extender creates the DTD_REF table when you enable a database for XML.
See Planning for XML columns and Planning for XML collections to learn more about using DTDs.
You can insert the DTD from the DB2 command shell or by using the administration wizard.