Welcome
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 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.
Programmer's Guide
The HCL® Informix® DataBlade® API Programmer's Guide describes information about the , 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.
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.

HCL Informix® V15.0.0 documentation
Welcome to the documentation for HCL Informix® 15.0.0 and related client tools and products.
Product overview
HCL Informix® is a fast and scalable database server that manages traditional relational, object-relational, and dimensional databases. Its small footprint and self-managing capabilities are suited to embedded data-management solutions.
Installing
These topics describe how to install HCL Informix® database servers, client products, and modules.
Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
Migrating and upgrading
You can upgrade to the 15.0.0 release of HCL Informix® or migrate from other database servers to Informix. Upgrading is an in-place migration method that uses your existing hardware and operating system software. Some changes to the Informix database server can affect upgrading from a previous release.
Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
Embedding Informix®
When you embed HCL Informix®, you can use enterprise-class high-availability and high performance with embeddability features such as easy programmability, a small disk and memory footprint, and silent deployment.
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 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 modules
  These topics describe how to use built-in database extensions and separately installed 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.
  - Programmer's Guide
    The HCL® Informix® DataBlade® API Programmer's Guide describes information about the , the C-language application programming interface (API) provided with HCL Informix.
    - 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 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 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.
  - Function Reference
    The IBM® Informix® DataBlade® API Function Reference describes the functions and the subset of functions that the supports.
  - Developers Kit
    The Developers Kit (DBDK) guides contain information about the tools you can use to develop and package modules, which extend the functionality of HCL Informix® databases.
  - J/Foundation Developer's Guide
    The HCL® 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 HCL® 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 HCL® 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 IBM® 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 IBM® 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 module.
Data warehousing
In addition to designing and implementing Informix® dimensional databases, you can use tools to create data warehouse applications and optimize your data warehouse queries.
Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
JSON compatibility
You can use the popular JSON-oriented query language created by MongoDB to interact with data stored in HCL Informix®.
Security
You can secure your Informix® database server and the data that is stored in your Informix databases. You can encrypt data, secure connections, control user privileges and access, and audit data security.
SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Troubleshooting HCL Informix®
Several troubleshooting techniques, tools, and resources are available for resolving problems that you encounter in your HCL Informix® database server environment.

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 syntax for the function is:

mint xa_start(XID *xid,   /* IN */
           mint rmid,     /* IN */
           int4 flags)   /* IN */

Table 1. The xa_start() parameters
Parameter	Description
xid	Pointer to the XID data structure that is defined in the xa.h file and used for the current transaction
rmid	Unique resource manager identifier
flags	`TMNOFLAGS`, which is the valid value

For valid return values, refer to X/Open information, including Distributed Transaction Processing: The XA Specification.

Currently, HCL Informix® does not call the xa_start() function because the XA data source must be created with the TMREGISTER flag.