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.
Create user-defined routines
Develop a user-defined routine
A C user-defined routine (UDR) is a UDR that is written in the C language and uses the server-side implementation of the to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. modules often include C UDRs that are made available for use by registering them in the database.
Creating UDR code
This section provides an overview of C UDR development.
Variable declaration
In a C UDR, you declare variables to hold information just as you would in a C function. The provides many data types for variable declaration.

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
    - Create user-defined routines
      - Develop a user-defined routine
        A C user-defined routine (UDR) is a UDR that is written in the C language and uses the server-side implementation of the to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. modules often include C UDRs that are made available for use by registering them in the database.
        Designing a UDR
        This section provides the following design considerations for the development of a C UDR: development tools, uses of a UDR, portability, and insert and update operations.
        Creating UDR code
        This section provides an overview of C UDR development.
        Variable declaration
        In a C UDR, you declare variables to hold information just as you would in a C function. The provides many data types for variable declaration.
        Session management
        Session management is different in a C UDR than in a client LIBMI application. Unlike a client LIBMI application, which can simultaneously connect to several databases, a UDR inherits a particular session context. That is, it is within an existing session and uses a database that is already opened.
        SQL statement execution
        The differences in the execution of SQL statements in a C UDR and a client LIBMI application are because of the differences in passing mechanisms that they use for the contents of an MI_DATUM structure. In a C UDR, you must consider the data type of the value in the MI_DATUM structure to determine how to obtain the value.
        Routine-state information
        When the routine manager executes a C UDR, it puts information about the routine sequence for the UDR in an MI_FPARAM structure and passes this MI_FPARAM structure as the last argument to the UDR.
        Event handling
        Your C UDR must perform event handling to ensure recovery from unexpected results, usually a warning or runtime error from the database server. To handle warnings and errors, the C UDR can define callback functions that the invokes when a particular event occurs.
        Well-behaved routines
        The most efficient way for a C UDR to execute is in the CPU virtual-process (CPU VP) class. However, to execute in the CPU VP, the UDR must be well-behaved. A well-behaved UDR adheres to a set of safe-code requirements that prevent the UDR from interfering with the efficient operation of the CPU VP.
        Compile a C UDR
        To compile a C UDR, use a C compiler to compile the source file (.c file extension) into an object file (.o file extension) and create a shared-object file that contains the object file.
        Register a C UDR
        The CREATE FUNCTION statement registers user-defined functions in the database. The CREATE PROCEDURE statement registers user-defined procedures in the database. These functions store information about the UDR in the sysprocedures system catalog table.
        Execute a UDR
        Debug a UDR
        Because a UDR runs as part of the database server process, the routine must not do anything that might negatively affect the running of the database server, such as exiting. This section provides information about how to use a C debugger to attach to a virtual processor, handle the debugging session of a C UDR, and use tracing.
        Change a UDR
        This section provides information about how to alter a C UDR and how to unload a shared-object file.
      - Write a user-defined routine
        This section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
      - Manage memory
        A C user-defined routine (UDR) has access to shared memory for dynamic allocations and stack memory for routine arguments (including the MI_FPARAM structure), local stack variables, and return values.
      - Create special-purpose UDRs
        This section describes how to create special UDRs, such as iterator functions, user-defined aggregates, and optimization functions.
      - Extend data types
        This section describes the ways to extend data types with C user-defined routines (UDRs).
    - 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.

Variable declaration

In a C UDR, you declare variables to hold information just as you would in a C function. The provides many data types for variable declaration.

The adds special prefixes to the names of its data types, as the following table shows.


data type	Data type prefix	More information
Data types to hold SQL data types	mi_	, C, and SQL data types
Data type structures that hold information for functions	MI_	data type structures

Correspondence of SQL data types to data types lists where in this publication each of the SQL data types is discussed in detail.

Use the data types for variable declaration in your C UDR even if there is a C-language equivalent. The data types are more portable if your C UDR moves to different computer architectures. For more information, see data types.