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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.
Event-handling mechanismsAn event-handling mechanism provides a way for one DataBlade® API module to inform another module (or another part of the same module) that an event has occurred during execution of a function.
Invoke a callbackA callback function (or just callback) is a function that you write to handle a particular event.
Register a callbackFor a callback to execute when its associated event occurs, you must register it with the mi_register_callback() function.
Types of callbacksThe second argument of the mi_register_callback() function is the event type. The DataBlade® API supports a type of callback for each event type.

Types of callbacks

The second argument of the mi_register_callback() function is the event type. The DataBlade® API supports a type of callback for each event type.

The following table lists the types of callbacks that the DataBlade API supports and the events that invoke them.


Callback type	Event type	More information
Exception callback	MI_Exception	Database server exceptions
Savepoint callback	MI_EVENT_SAVEPOINT	State-transition events
Commit-abort callback	MI_EVENT_COMMIT_ABORT	State-transition events
Post-transaction callback	MI_EVENT_POST_XACT	State-transition events
End-of-statement callback	MI_EVENT_END_STMT	State-transition events
End-of-transaction callback	MI_EVENT_END_XACT	State-transition events
End-of-session callback	MI_EVENT_END_SESSION	State-transition events
State-change callback	MI_Xact_State_Change	State-transition events
Client LIBMI callback	MI_Client_Library_Error	Client LIBMI errors

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