The routines that you write must be written in a language which conforms to the calling and operational conventions of the C language. If you use a language other than C, be sure that the structures you build have the same structure, on a field-by-field basis, as those defined in the header file, IIADD.H. For the location of this header file, see the chapter "Introducing Object Management Extension."

To avoid problems, your code must follow these guidelines:

The code must not make any system calls or perform any other operation, such as generating exceptions or signals, which alter the flow of control within the server.

The code must not perform any operations such as memory allocations or operations such as disk I/O, which cause the process to be suspended.

The code must perform only computations on the data provided by the DBMS Server.

User-defined data types are visible only to the DBMS Server. When a user-defined data type is returned to an Ingres tool such as Query-By-Forms, the DBMS Server must convert your new data type to a standard SQL data type. To specify the external data type, use the dbtoev routine. For more information, see dbtoev in the "Defining Data Types" chapter.