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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.
State-transition eventsWhen the database server raises a state-transition event, the database server invokes any callbacks registered for the state transition. This section provides information about state-transition handling in DataBlade® API modules, including an explanation of state-transition events and a description of how to handle a state-transition event in a C UDR and a client LIBMI application.
Understanding state-transition eventsState-transition events occur when the database server changes its processing state. The DataBlade® API represents a state transition as one of the enumerated values of the MI_TRANSITION_TYPE data type.

Understanding state-transition events

State-transition events occur when the database server changes its processing state. The DataBlade® API represents a state transition as one of the enumerated values of the MI_TRANSITION_TYPE data type.

The following table shows the transitions in the server-processing state and the corresponding MI_TRANSITION_TYPE values.


State-transition type	Description
MI_BEGIN	The database server is beginning a new transaction.
MI_NORMAL_END	The database server just completed the current event successfully.
MI_ABORT_END	The database server just rolled back the current event. (The statement failed, or the transaction was aborted or rolled back.)

The milib.h header file defines the MI_TRANSITION_TYPE data type and its state-transition values.

The following table shows the state-transition types and the state-transition events that they can cause.


State-transition type	Event in client LIBMI application	Event in C UDR
Begin transaction or savepoint (MI_BEGIN)	MI_Xact_State_Change	None
Event end: commit (MI_NORMAL_END)	MI_Xact_State_Change	MI_EVENT_SAVEPOINT MI_EVENT_COMMIT_ABORT MI_EVENT_POST_XACT MI_EVENT_END_STMT MI_EVENT_END_XACT MI_EVENT_END_SESSION
Event end: rolled back (MI_ABORT_END)	MI_Xact_State_Change	MI_EVENT_SAVEPOINT MI_EVENT_COMMIT_ABORT MI_EVENT_POST_XACT MI_EVENT_END_STMT MI_EVENT_END_XACT MI_EVENT_END_SESSION

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