Application Building Guide

Other Migration Considerations

Consider the following points when you develop your applications. They will help make your applications portable:

• On UNIX, use only the default path, /usr/lib:/lib, in your applications. On OS/2 and Windows 32-bit operating systems, ensure the LIB environment variable points to %DB2PATH%\lib by using:

     set LIB=%DB2PATH%\lib;%LIB%
  

  Also, create symbolic links between the default path and the version of DB2 you are using. Ensure that the link is to the minimum level of DB2 required by your applications. Refer to the Quick Beginnings book for your platform for information about setting links.

• If your application requires a particular version of DB2, code the path that specifies the DB2 version in your application. For example, if your AIX application requires DB2 Version 5, code /usr/lpp/db2_05_00/lib. Ordinarily, you do not need to do this.
• When you are building an application for production, rather than internal development, the path in your application should not point to the instance owner's copy of the sqllib/lib directory on UNIX, or the %DB2PATH%\lib directory on OS/2 and Windows 32-bit operating systems. This makes applications highly dependent on specific user names and environments.
• Generally, do not use the LIBPATH environment variable, or the LIB environment variable on Windows 32-bit operating systems, to alter search paths in a particular environment. The variable overrides the search paths specified in the applications running in that environment. Applications might not be able to find the libraries or the files that they need.
• In DB2 Universal Database Versions 6.1 and 7.1, all character array items with string semantics have type char, instead of other variations, such as unsigned char. Any applications you code with DB2 Universal Database Version 6.1 or Version 7.1 should follow this practice.

  If you have DB2 Version 1 applications which use unsigned char, your compiler might produce warnings or errors because of type clashes between unsigned char in Version 1 applications and char in Version 6.1 or Version 7.1 function prototypes. If this occurs, use the compiler option -DSQLOLDCHAR to eliminate the problem.

• Refer to the SQL Reference for a list of incompatibilities between DB2 Universal Database Version 7.1 and previous versions of DB2. Refer to the Administrative API Reference for a list of API incompatibilities between DB2 Universal Database Version 7.1 and previous versions of DB2.