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.
overview
Access SQL data types
This section provides an overview of the data types that the supports.
The NULL constant
The supports two different uses of a NULL constant: the SQL NULL value and the NULL-valued pointer. The NULL-valued pointer is not the same as the SQL NULL value.

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
      - The
        The HCL Informix® is the application programming interface (API) for HCL Informix. You can use functions in modules to access data stored in the Informix database.
      - Access SQL data types
        This section provides an overview of the data types that the supports.
        Type identifiers
        A type identifier, MI_TYPEID, is a data type structure that identifies a data type uniquely. For extended data types, the type identifier is database-dependent; that is, the same type identifier might identify different data types for different databases.
        Type descriptors
        A type descriptor, MI_TYPE_DESC, is a data type structure that contains information about an SQL data type. For built-in data types, this information comes from the syscolumns table. For extended data types, it contains the information in the sysxtdtypes table.
        Character data types
        Varying-length data type structures
        A varying-length data type structure can hold data whose length varies from one instance to the next. The database server uses varying-length structures extensively to manage data transfer for modules.
        Byte data types
        Boolean data types
        Boolean data holds values to indicate two states: true and false. The provides support for boolean values in both their text and binary representations.
        Simple large objects
        The does not provide direct support for simple large objects. Therefore, it cannot directly access TEXT and BYTE columns. However, the database server provides the following cast functions between simple and smart large objects.
        The MI_DATUM data type
        The handles a generic data value as an MI_DATUM value, also called a datum. A datum is stored in a chunk of memory that can fit into a computer register.
        The NULL constant
        The supports two different uses of a NULL constant: the SQL NULL value and the NULL-valued pointer. The NULL-valued pointer is not the same as the SQL NULL value.
        SQL NULL value
        The SQL NULL value represents a null or empty value in a database column. The NULL value is distinct from all valid values for a given data type.
        NULL-valued pointer
        The NULL-valued pointer, as defined in the stddef.h header file, is a constant that represents an initialized pointer.
    - Data manipulation
    - Database access
    - 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 NULL constant

The supports two different uses of a NULL constant: the SQL NULL value and the NULL-valued pointer. The NULL-valued pointer is not the same as the SQL NULL value.