NLS_LANG
To display characters properly SQL*Plus (character mode version) needs to know the character set being used to display its output on the client. A setting called NLS_LANG controls this. NLS_LANG has three components -- language, territory, and character set. Any one, two, or three of these components can be specified in an NLS_LANG settings. Here are some examples.
| NLS_LANG Setting | Components That Are Set |
|---|---|
American |
Language |
_America |
Territory |
.AL32UTF8 |
Character Set |
American_America |
Language, Territory |
American.AL32UTF8 |
Language, Character Set |
American_America.AL32UTF8 |
Language, Territory, Character Set |
It is important to note the following.
- NLS_LANG identifies the character set used by the client, not the server
- NLS_LANG cannot be changed via an ALTER SESSION command (though the language and territory components can be overridden with ALTER SESSION SET NLS_LANGUAGE or ALTER SESSION SET NLS_TERRITORY)
To determine a session's NLS_LANG setting SQL*Plus either uses the value stored in the operating system's NLS_LANG environment variable or, if no such variable exists, it defaults to US7ASCII.
On UNIX/Linux systems when the session's locale codeset is set to UTF-8 then NLS_LANG's character set component should be set to AL32UTF8, which is Oracle's UTF-8 character set. See Unicode on UNIX for more information about the UNIX "locale" feature and Oracle.
Spool Files
SQL*Plus spool files are created using the encoding associated with the NLS_LANG character set.