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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Database access
Exceptions and eventsThis section describes exceptions and events, and explains how to handle them in DataBlade® API modules.
Callback functionsTo catch or handle an event, you create a C function called a callback function. In your DataBlade® API module, you can register callback functions to handle recovery from events. The DataBlade® API invokes a registered (and enabled) callback when the event associated with the callback occurs.
Declare a callback functionTo declare a callback function, you provide the MI_CALLBACK_STATUS return type, the optional MI_PROC_CALLBACK modifier, and the parameter declarations.

Declare a callback function

To declare a callback function, you provide the MI_CALLBACK_STATUS return type, the optional MI_PROC_CALLBACK modifier, and the parameter declarations.

The following figure shows the declaration of a callback function named myhandler() for use in a UDR.

begin figure description - This figure is described in the surrounding text. - end figure description — Figure 1: A sample callback declaration

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