Home
Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
ESQL/C Guide
The Informix® ESQL/C Programmer's Manual explains how to use Informix ESQL/C, the Informix implementation of Embedded Structured Query Language (SQL) for C (ESQL/C), to create client applications with database-management capabilities.
Dynamic SQL
Using dynamic SQL
A database cursor
A database cursor is an identifier associated with a group of rows. It is, in a sense, a pointer to the current row in a buffer.
Optimize cursor execution
Automatically freeing a cursor
Enable the AUTOFREE feature

Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
- Change Data Capture API Programmer's Guide
  The Informix® Change Data Capture API Programmer's Guide describes how to program applications to process changed data from HCL Informix databases using the Informix Change Data Capture API.
- Embedded SQLJ for HCL Informix®
  The Informix® Embedded SQLJ User's Guide contains information about using Informix Embedded SQLJ.
- ESQL/C Guide
  The Informix® ESQL/C Programmer's Manual explains how to use Informix ESQL/C, the Informix implementation of Embedded Structured Query Language (SQL) for C (ESQL/C), to create client applications with database-management capabilities.
  - What is Informix® ESQL/C?
  - Database server communication
  - Dynamic SQL
    - Using dynamic SQL
      - Execute dynamic SQL
      - A database cursor
        A database cursor is an identifier associated with a group of rows. It is, in a sense, a pointer to the current row in a buffer.
        Receive more than one row
        Send more than one row
        Name the cursor
        Optimize cursor execution
        Size the cursor buffer
        The cursor buffer is the buffer that the Informix® ESQL/C application uses to hold the data (except simple large-object data) in a cursor.
        Automatically freeing a cursor
        Enable the AUTOFREE feature
        The SET AUTOFREE statement
        You can use the SQL statement, SET AUTOFREE, to enable and disable the AUTOFREE feature.
        Defer execution of the PREPARE statement
      - The collect.ec program
      - Optimize OPEN, FETCH, and CLOSE
      - Using OPTOFC and Deferred-PREPARE together
        To achieve the most optimized number of messages between the client application and the database server, use the Optimize OPEN, FETCH, CLOSE feature, and the Deferred-PREPARE feature together.
      - SQL statements that are known at compile time
      - SQL statements that are not known at compile time
        An SQL statement that is not known at compile time is usually one that the user enters in an interactive application.
    - Determine SQL statements
      If you do not know until run time what SQL statement to execute, you can dynamically determine that statement with the DESCRIBE statement and use a dynamic-management structure to hold any values that the statement sends to or receives from the database server.
    - A system-descriptor area
      A system-descriptor area is a dynamic-management structure that can hold data that a prepared statement either returns from or sends to the database server. A system-descriptor area conforms to X/Open standards.
    - An sqlda structure
      An sqlda structure is a dynamic-management structure that can hold data that is either returned from or sent to the database server by a prepared statement. It is a C structure defined in the sqlda.h header file.
  - Appendixes
    This section contains additional reference information.
- GLS User's Guide
  The Informix® GLS User's Guide describes the Global Language Support (GLS) feature available in Informix products.
- API
  The Informix® GLS API Programmer's Guide describes the global language support (GLS) application programming interface (API) available in Informix ESQL/C and HCL Informix DataBlade® modules.
- Informix® Object Interface for C++ Guide
  The Informix® Object Interface for C++ Programmer's Guide describes how to develop HCL Informix client applications by using the object-oriented C++ programming language.
- Informix® ODBC Driver Guide
  The Informix® ODBC Driver Programmer's Manual serves as a user guide and reference for Informix ODBC Driver, which is the Informix implementation of the Microsoft™ Open Database Connectivity (ODBC) interface, Version 3.0.
- .NET provider options
  The Data Server Provider for .NET DB2® provider option is the preferred Informix® provider for developing new applications.
- Informix® JDBC Driver Guide
  The Informix® JDBC Driver Programmer's Guide describes how to install, load, and use Informix JDBC Driver to connect to the Informix database from within a Java™ application or applet.
- Informix International Language Supplement (ILS) User Guide
  These topics include information about the translated user interface files for Informix® UNIX™ products, locales, and code set conversion tables
- Informix® OLE DB Provider Guide
  The Informix® OLE DB Provider Programmer's Guide describes the software requirements for using Informix OLE DB Provider, show how to install and configure the provider for your use, and explain how to use Informix OLE DB Provider to enable client applications, such as ActiveX Data Object (ADO) applications and web pages, to access data on the Informix server.

Enable the AUTOFREE feature

You can enable the AUTOFREE feature for the Informix® ESQL/C application in either of the following ways:

Set the IFX_AUTOFREE environment variable to 1.
When you use the IFX_AUTOFREE environment variable to enable the AUTOFREE feature, you automatically free cursor memory when cursors in any thread of the program are closed.
Execute the SQL statement, SET AUTOFREE.
With the SET AUTOFREE statement, you can enable the AUTOFREE feature for a particular cursor. You can also enable or disable the feature in a particular connection or thread.

Important: Be careful when you enable the AUTOFREE feature in legacy Informix® ESQL/C applications. If a legacy application uses the same cursor twice, it generates an error when it tries to open the cursor for the second time. When the AUTOFREE feature is enabled, the database server automatically frees the cursor when it closes it. Therefore, the cursor does not exist when the legacy application attempts to open it a second time, even though the application does not explicitly execute the FREE statement.

For more information about the IFX_AUTOFREE environment variable, see the Informix® Guide to SQL: Reference.