Examples and limits of BYTE and CHAR semantics usage (NLS_LENGTH_SEMANTICS) (Doc ID 144808.1)

Last updated on JUNE 13, 2023

Applies to:

Oracle Database Backup Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database - Enterprise Edition - Version 9.0.1.0 to 12.2.0.1 [Release 9.0.1 to 12.2]
Oracle Database - Standard Edition - Version 9.0.1.0 and later
Oracle Database Cloud Schema Service - Version N/A and later
Information in this document applies to any platform.

Purpose

To document best practices, limits and details when implementing NLS_LENGTH_SEMANTICS as BYTE or CHAR.

Scope

Any DBA wanting to use NLS_LENGTH_SEMANTICS.

NLS_LENGTH_SEMANTICS allows you to specify the length of a column datatype in terms of CHARacters rather than in terms of BYTEs. Typically this is when using an AL32UTF8 or other varying width NLS_CHARACTERSET database where one character is not always one byte. While using CHAR semantics has as such no added value in a 7/8 bit characterset it's fully supported so any application code / table setup using CHAR can also be used in a 7/8bit characterset like US7ASCII/WE8MSWIN1252.
This parameter is a 9i (and up) feature and is not available in older releases.

Make sure to check also "Things to know when using CHAR semantics:" as there are certain limitations on when you can use this.