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
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.
Virtual processors
To service multiple client-application SQL requests, the database server uses virtual processors (VPs). The database server breaks the SQL request into distinct tasks, based on the resource that the task requires. Different VP types, called virtual-processor classes (VP classes), service the different kinds of tasks.
Create a well-behaved routine
Define a user-defined VP
You define a new virtual-processor class in the onconfig file with the VPCLASS configuration parameter.
Define a yielding user-defined VP class

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.
      - 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.
        Code a C UDR
        When you code a C UDR, you define routine parameters, obtain argument values, define a return value, and code the routine body to write a C function.
        Virtual processors
        To service multiple client-application SQL requests, the database server uses virtual processors (VPs). The database server breaks the SQL request into distinct tasks, based on the resource that the task requires. Different VP types, called virtual-processor classes (VP classes), service the different kinds of tasks.
        Create a well-behaved routine
        Preserving availability of the CPU VP
        A well-behaved C UDR must preserve the availability of the CPU virtual processor (CPU VP).
        Write threadsafe code
        A well-behaved C UDR must be threadsafe.
        Avoid restricted system calls
        Choose the user-defined VP class
        Define a user-defined VP
        You define a new virtual-processor class in the onconfig file with the VPCLASS configuration parameter.
        Define a yielding user-defined VP class
        Define a nonyielding user-defined VP class
        To create a nonyielding user-defined VP, include the noyield option of the VPCLASS configuration parameter. You can also use the num option to specify the number of VPs in the nonyielding user-defined VP class.
        Define a single-instance user-defined VP class
        To define a single-instance user-defined VP, specify a value of one for the num option of the VPCLASS configuration parameter.
        Assign a C UDR to a user-defined VP class
        Manage virtual processors
        To manage virtual processors, you need to initialize VP classes, add and drop VPs, and monitor VPs.
        Control the VP environment
        The routine manager executes your C UDR in a virtual-processor (VP) environment.
        Perform input and output
        Because a C UDR executes in the context of the database server, it must not use the standard input/output (I/O) calls such as scanf() and printf(). The provides support for I/O on a generic stream and I/O on an operating-system file from a UDR.
        Access the UDR execution environment
      - 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.

Define a yielding user-defined VP class

The VPCLASS configuration parameter creates a yielding user-defined VP by default. You can also use the num option to specify the number of VPs in the yielding user-defined VP class.

The following code fragment defines a yielding user-defined VP class named newvp with three virtual processors.

VPCLASS newvp,num=3               # Yielding VP class with 3 instances

The C user-defined function, GreaterThanEqual(), in the code fragment in ids_dapip_0687.html#ids_dapip_0687, executes in the newvp VP class.