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Administration Guide

Performance Considerations and Character Conversion

When your application and database are not using the same code page, a mapping of the data from one code page to the other code page takes place, if possible. To properly map data between application and database code pages, some data conversion may be required.

This mapping and data conversion introduce a certain amount of overhead into the processing time for applications that are running in a code page that is different from the database code page. Your application's performance can be improved if the application and database are using the same code page or the identity collating sequence.

Character conversion can occur in the following situations:

Character conversion will not occur for:

For more information about EUC code page support and National Language Support (NLS) considerations, see the Appendix O. "National Language Support (NLS)" appendix later in this book.

Depending on the operating system environment DB2 database managers use a conversion function and conversion tables, or DBCS conversion APIs, when converting multi-byte code pages.
Note:Character string conversions between multi-byte code pages, like DBCS with EUC, may result in either an increase or a decrease in the length of the string.

Code points assigned to different characters in a country's PC DBCS, EUC, and UCS-2 code sets may produce different results when sorting the same characters. If sorting is required across code sets for different countries, you should see the Appendix O. "National Language Support (NLS)" appendix later in this book.

Extended UNIX Code (EUC) Code Page Support

Use of host variables that use graphic data in C or C++ applications require special considerations including special precompiler, application performance, and application design issues.

If applications are developed requiring EUC code sets, you should see the API Reference manual.

Database and client application support for graphic (that is, double byte character) data must overcome the two bytes wide restriction when dealing with many characters found in both the Japanese and Traditional Chinese EUC code pages. Graphic data from these EUC code pages is stored and manipulated using the UCS-2 code set.

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