An External Stored Procedure is written in a language other than SQL, and is defined by the ANSI SQL: 1999 standard. ODBC support of External Stored Procedures (XSP) is transparent to the ODBC user, and should have no effect on existing user applications.
The full specification of the syntax, format, and rules for both creating and invoking XSPs is beyond the scope of this document. See Teradata Vantage™ - SQL External Routine Programming, B035-1147 for details on how to create and invoke user-defined functions.
XSPs are similar to UDFs except the CALL statement is used in the same manner as a stored procedure to invoke an XSP.