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.
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.
Design decisions
These topics present the choices that you make to optimize the performance and flexibility of the access method that you can create with the virtual-index interface (VII).
Support for data retrieval, manipulation, and return
This topic affects the design of am_getnext, am_insert, am_delete, and am_update.
Converting to and from a row format

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.
  - 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.
    - Access methods
      This section describes access methods, explains why you create user-defined access methods, and shows you how to create user-defined access methods
    - Develop an access method
      These topics describe the steps that you take to implement a user-defined access method with the Virtual-Index Interface (VII).
    - Design decisions
      These topics present the choices that you make to optimize the performance and flexibility of the access method that you can create with the virtual-index interface (VII).
      - Store data in shared memory
        The access method can allocate areas in shared memory to preserve information between purpose-function calls. To allocate memory, you decide which function to call and what duration to assign.
      - Access database and system catalog tables
      - No label-based access control on virtual indexes
        You cannot have label-based access control on tables with virtual indexes.
      - Execute a UDR across databases of the same database server instance
        The database server supports built-in opaque parameters in functional indexes and Virtual-Index Interfaces across multiple databases of the same database instance. You can implicitly and explicitly execute a UDR (written in SPL, C, or Java™) across databases with built-in data types and user-defined distinct types whose base types are built-in data type parameters and return types.
      - Handle the unexpected
        The access method can respond to events that the database server initiates, and to errors in requests for access-method features that the database server cannot detect.
      - Data definition statements
      - Support multiple-column index keys
      - Using FastPath
      - Process queries that involve a virtual index
        This section describes various options for processing a SELECT statement, or query, that involves a virtual index.
      - Enhancing performance
        To enhance performance, the access method can take advantage of executing parallel scans, inserts, deletes, and updates; bypassing tables scans; and buffering multiple rows.
      - Support for data retrieval, manipulation, and return
        This topic affects the design of am_getnext, am_insert, am_delete, and am_update.
        Enforcing unique-index constraints
        The UNIQUE or DISTINCT keyword in a CREATE INDEX or insert statement specifies that a secondary access method cannot insert multiple occurrences of a key value. The UNIQUE or DISTINCT keyword in a SELECT statement specifies that the access method must return only one occurrence of a key value.
        Check isolation levels
        The isolation level affects the concurrency between sessions that access the same set of data.
        Converting to and from a row format
        Determine transaction success or failure
      - Supply error messages and a user guide for your functions
        Plan the user-guide and error messages for the access-method purpose functions that you are providing.
    - Purpose-function reference
      These topics describe the purpose functions that the access-method developer provides.
    - Descriptor function reference
    - SQL statements for access methods
      These topics describe the syntax and usage of the ALTER ACCESS_METHOD, CREATE SECONDARY ACCESS_METHOD, and DROP ACCESS_METHOD statements, which insert, change, or delete entries in the sysams system catalog table.
    - XA-compliant external data sources
      The HCL Informix® Transaction Manager recognizes XA-compliant external data sources, which can participate in two-phase commit transactions.
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.

Converting to and from a row format

Before you begin

Before the access method can return row values to a query, the access method must convert source data to data types that database server recognizes.

About this task

To create a row:

Procedure

Call mi_tab_rowdesc() to retrieve the row descriptor.
Call the appropriate row-descriptor accessor functions to obtain the information, such as data type, for each column.
For a list of available row-descriptor accessor functions, see the description of MI_ROW_DESC in the HCL® Informix® DataBlade® API Programmer's Guide.
If necessary, convert external data types to types that the database server recognizes.
Set the value of the columns that the query does not need to NULL.
Call the mi_row_create() function to create a row from the converted source data.

What to do next

Tip: The mi_row_create() function can affect performance because it requires database server resources. Use it only if you set the am_keyscan purpose flag for the access method.

The database server passes an MI_ROW structure to the am_insert and am_update purpose functions. To extract the values to insert or update, call mi_value() or mi_value_by_name(). For more information about these functions, see the HCL® Informix® DataBlade® API Programmer's Guide.