DOCUMENTATION NOTES FOR

IBM Informix ESQL/C Programmer's Manual

Date: 06/2003

Version: 9.53


I. Overview

This document describes feature and performance topics not covered in the IBM Informix ESQL/C Programmer's Manual or modified since publication.


II. Using GLU (GLS for Unicode) Interface Functions

By default, the use of GLU is turned off. GLS will use the locale files for Unicode and GB18030-2000. The primary reason for this is that C++ linker is required in order to use ICU. This will have a wide impact on both existing and new applications. Existing applications will have to be re-linked using C++ and all new applications will require a C++ linker. Turning GLU off by default mitigates this condition.

There are two methods to use the GLU functions in and ESQL/C application.

Using the -glu compiler flag

When compiling an ESQL/C application, you can use the -glu flag to invoke the GLU functions as in the following example:

esql -o try -glu try.ec ...

Using the GL_USEGLU environment variable

You can also invoke the GLU functions by setting the GL_USEGLU environment variable to 1. You can then compile ESQL/C programs without specifying the -glu flag.

setenv GL_USEGLU 1

esql -o try.ec ...

III. Enhanced Functionality of the DESCRIBE Statement

IBM Informix Dynamic Server, Version 9.40 provides enhanced functionality of the DESCRIBE statement. This allows you to use the WHERE clause as an input parameter in INSERT and UPDATE statements. The following new syntaxes are supported:

EXEC SQL DESCRIBE [OUTPUT] <statement-name descriptor>

EXEC SQL DESCRIBE INPUT <statement-name descriptor>

IV. New Environment Variables

a. IFX_PAD_VARCHAR: When this environment variable is set to 1, the client sends the varchar datatype with padded trailing spaces. When this environment is not set(default)the client sends varchar datatype value without trailing. This environment IFX_PAD_VARCHAR needs to be set only at the client side and is supported only with IBM Informix ESQL/C Version 9.53 or above and IBM Informix Dynamic Server Version 9.40 or above.

b. BIG_FET_BUF_SIZE: This is an enhancement of FET_BUF_SIZE to support cursor buffers greater than 32,769 but less than or equal to 4MB. This environment variable is supported only for Extended Parallel Server, Version 8.40.UC1 and higher.

c. BLANK_STRINGS_NOT_NULL: When this environment is set to 1 the string host variable stores an empty string as a single blank followed by a null terminator. When this environment variable is not set, a string host variable stores an empty string as null. This environment variable is provided to support backward compatibility for 7.x against string host variables and needs to be set only at client side.

V. PAM Support

Beginning with ESQL/C 9.53.UC2, ESQL/C will support the Pluggable Authentication Module (PAM) method for client-server authentication. Users who use this feature will need to re-write their client applications and would need to have a callback function registered in their application to support the challenge-response mechanism that this feature supports.

An example of the use of the callback function is available as a demo shipped with ESQL/C by the name of pamdemo.ec



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