Saturday, April 23, 2011

Oracle NLS_LANG Setting for Language/Territory/Character Set

Setting NLS_LANG tells Oracle what characterset the client is using so that  Oracle can do conversion if needed from client’s characterset to the database characterset and setting this parameter on the client does not change the client’s characterset. Setting Language and Territory in nls_lang has nothing to do with storing characters in database, it’s controlled by the characterset and of course if the database can store that characterset..Below is the syntax of setting   NLS_LANG .

NLS_LANG=<language>_<territory>.<character set>
Example:  NLS_LANG= BRAZILIAN PORTUGUESE_BRAZIL.WE8MSWIN1252

To  check session  NLS   session  parameters,( note this doesn’t return the characterset set by NLS_LANG)

SQL> select  *   from   nls_session_parameters ;


To find the NLS_LANG of the database one can run the following SQL:
SQL>select DECODE(parameter, 'NLS_CHARACTERSET', 'CHARACTER SET','NLS_LANGUAGE',    'LANGUAGE', 'NLS_TERRITORY', 'TERRITORY') name, value from v$nls_parameters WHERE parameter IN ( 'NLS_CHARACTERSET', 'NLS_LANGUAGE', 'NLS_TERRITORY');
Sample Output :
NAME                             VALUE
------------          -------------------
LANGUAGE                  AMERICAN
TERRITORY                 AMERICA
CHARACTER SET        WE8MSWIN1252


Setting  NLS_LANG for export/import  :  we encounter character set conversion problems during exporting or importing a database or table(s) then we should check the following information to confirm whether the export/import procedure was performed correctly . 

When exporting/importing one can minimize risk of losing data during import/export by setting NLS_LANG.


1.)  Before starting export set  NLS_LANG to be the same character set of the database being exported which means no conversion takes place, all the data will be stored in the export file as it was stored in the database.
2.) Before starting import set NLS_LANG to be the same value as the it was set during export which means no conversion will take place in the import session, but if the character set of the target database is different the data will automatically be converted when import inserts the data in the database.
3.)  Before starting export set NLS_LANG to be the same character set of the database being imported to which means conversion takes place at this step it will automatically convert during export.
4.) Before starting import set NLS_LANG to be the same value as the it was set during import which means no conversion will take place as it was already converted during export.
5.) Settings on the machine from which u are trying to take the import of the data.Even though the NLSCHAR AND NLS NCHA Settings on the source and destination databases are same unless the console from where u are trying to take export and import also should same other wise u will get all the junk characters .
6.)  Sometimes we make import  and  get  some special character  ( like ?,! )  that means, we need to go 'region settings' and change the location (say)  ”brazil"  and default language make as   “ brazil” . (if we are importing American to brazil).
7.) check  the  export  log file and see what is specified.




Enjoy          J J J



No comments: