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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 extensions
You 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 Guide
The 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
XA-compliant external data sources
Create user-defined XA-support routines
You can create user-defined XA-support routines, such as xa_open(), xa_start(), xa_prepare(), xa_rollback(), xa_commit(), xa_recover(), xa_complete(), xa_forget(), xa_close(), and xa_end(). These purpose functions are used for transaction management.

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.
- Informix® extensions and DataBlade® modules
  These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
- Creating extensions
  You 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 Guide
    The Informix® DataBlade® API Programmer's Guide describes information about the DataBlade API, the C-language application programming interface (API) provided with HCL Informix.
    - DataBlade® API overview
    - Data manipulation
    - Database access
      - Connection handling
        This section describes how to initialize, establish, and close connections.
      - Execute SQL statements
        One basic task of a DataBlade® API module is to send SQL statements to the database server for execution.
      - Execute user-defined routines
        This section provides information about how to call a user-defined routine (UDR).
      - Exceptions and events
        This section describes exceptions and events, and explains how to handle them in DataBlade® API modules.
      - XA-compliant external data sources
        Overview of integrating XA-compliant data sources in transactions
        The transaction manager, which is an integral part of the database server, not a separate module, can invoke support routines for each XA-compliant, external data source that participates in a distributed transaction at a particular transactional event, such as prepare, commit, or rollback. This interaction conforms to X/Open XA interface standards.
        Create user-defined XA-support routines
        You can create user-defined XA-support routines, such as xa_open(), xa_start(), xa_prepare(), xa_rollback(), xa_commit(), xa_recover(), xa_complete(), xa_forget(), xa_close(), and xa_end(). These purpose functions are used for transaction management.
        The xa_open() function
        The xa_open() function is called once per database session for each XA data source that participates in the HCL Informix® transaction. The xa_open() function is called when a user-defined function registers the XA data source with a transaction by calling mi_register_xadatasource() or using ax_reg() for the first time after the database opens.
        The xa_close() function
        When the database is closed or the session ends, which ever occurs first, HCL Informix® calls the xa_close() function for each XA data source used in the database session. This occurs when a new local database is opened, a database is closed, or a client session ends. The xa_close() function is also called when the XA data source is created and registered in a transaction and the transaction is rolled back.
        The xa_start() function
        In each transaction, when an XA data source registers statically with the HCL Informix® transaction, HCL Informix runs the xa_start() function.
        The xa_end() function
        For each XA data source participating in a transaction, the xa_end() function is called before a direct rollback or before the prepare stage for a commit operation.
        The xa_prepare() function
        The xa_prepare() function prepares XA data source transaction changes for a commit or rollback operation. A successful return from xa_prepare() indicates that the XA data source will successfully commit or rollback when requested.
        The xa_rollback() function
        The xa_rollback() function is called if an application rolls back the transaction or if the prepare stage of the transaction fails.
        The xa_commit() function
        The xa_commit() function requests each participating XA data source to commit a transaction. If all of the XA data sources return TMSUCCESS on calls to xa_end() and to xa_prepare(), the database server calls xa_commit() on each participating XA data source.
        The xa_recover() function
        The xa_recover() function obtains a list of prepared transaction branches from a resource manager.
        The xa_forget() function
        The xa_forget() function enables an XA data source to disregard an heuristically completed transaction.
        The xa_complete() function
        The xa_complete() function waits for an asynchronous operation to complete. If an operation is still pending, xa_complete() waits for the completion and returns the status.
        Create and drop XA data sources and data source types
        This section contains information about creating and dropping XA-compliant data source types and instances of XA-compliant data sources.
        Register and unregister XA-compliant data sources
        After you create an external XA-compliant data source, transactions can register data source using the mi_xa_register_xadatasource() or ax_reg() functions. You can also unregister the data source using the mi_xa_unregister_xadatasource() or ax_unreg() functions.
        Monitor integrated transactions
    - Create user-defined routines
    - Appendix
      This section contains additional reference information.
  - DataBlade® API Function Reference
    The Informix® DataBlade® API Function Reference describes the DataBlade API functions and the subset of Informix ESQL/C functions that the DataBlade API supports.
  - DataBlade® Developers Kit
    The DataBlade® Developers Kit (DBDK) guides contain information about the tools you can use to develop and package DataBlade modules, which extend the functionality of HCL Informix® databases.
  - J/Foundation Developer's Guide
    The J/Foundation Developer's Guide describes how to write user-defined routines (UDRs) in the Java™ programming language for Informix®.
  - R-Tree Index User's Guide
    The Informix® R-Tree Index User's Guide describes the HCL Informix R-tree secondary access method and how to access and use its components.
  - User-Defined Routines and Data Types Developer's Guide
    The Informix® User-Defined Routines and Data Types Developer's Guide describes how to define new data types and enable user-defined routines (UDRs) to extend HCL Informix.
  - Virtual-Table Interface Guide
    The Informix® Virtual-Table Interface Programmer's Guide explains how to create a primary access method with the Virtual-Table Interface (VTI) so that users have a single SQL interface to HCL Informix tables and to data that does not conform to the storage scheme of HCL Informix.
  - Virtual-Index Interface Guide
    The Informix® Virtual-Index Interface Programmer's Guide explains how to create a secondary access method with the Virtual-Index Interface (VII) to extend the built-in indexing schemes of HCL Informix typically with a DataBlade® module.

Create user-defined XA-support routines

You can create user-defined XA-support routines, such as xa_open(), xa_start(), xa_prepare(), xa_rollback(), xa_commit(), xa_recover(), xa_complete(), xa_forget(), xa_close(), and xa_end(). These purpose functions are used for transaction management.

You use these functions when you create XA data source types for external XA-compliant data sources.

Important: Even though HCL Informix® does not call all of the routines described in this section, you must have the routines to use as parameters when you create an XA data source type. In the CREATE XADATASOURCE TYPE statement, all of the parameters are mandatory.

There is no reason to run these functions directly from SQL or from user-defined routines.

The functions that you create must follow X/Open XA standards.

Important: You cannot drop an XA support user-defined routine until all of the XA data source types that use the support function are dropped.