DBCALAD is only used by the DBCHCL Initiate-request and Initiate-with-protocol-function functions: it is ignored by other DBCHCL functions. It is of fixed length, is not initialized by DBCHINI, and is allocated by the application.
When the DBCAREA LOB-aggregate-data-pointer field is not zero, it points to one DBCALAD extension; when zero, no DBCALAD extension exists for the request. The LAD overrides specifications in Teradata SQL that defer data for a Large-object (such specifications as either a column specified AS DEFERRED <BY NAME> in the USING row descriptor of the Teradata SQL statement, or with a DEFERRED datatype in a DataInfoX or StatementInformation parcel for a parameterized SQL statement), providing data for such objects in the request itself.
The prologue for the Assembler, COBOL, C, and PL/I mappings of the DBCALAD provides language-dependent information in constructing the extension and should be consulted.
The application should set unused fields to binary zeroes, allowing successful execution of existing applications should these fields ever be used.