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Changing Or Choosing the Database Character Set ( NLS_CHARACTERSET ) (Doc ID 225912.1)

Last updated on APRIL 22, 2022

Applies to:

Oracle Database - Standard Edition - Version and later
Oracle Database - Enterprise Edition - Version and later
Oracle Database Cloud Schema Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.



Anyone trying to change the NLS_CHARACTERSET.

There are still "dba's" out there who try to change the NLS_CHARACTERSET or NLS_NCHAR_CHARACTERSET by updating props$ .
This is NOT supported and WILL corrupt your database. This is one of the best way's to destroy a complete dataset.

The first step to take if this is done is a complete restore of the database.
If no backup is available Oracle Support will TRY to help you out of this but Oracle will NOT warrant that the data can be recovered or recovered data is correct and you WILL be asked to do a FULL export and a complete rebuild of the database.

Please, do NOT update props$.


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In this Document
 A) The database character set (NLS_CHARACTERSET)
 B) Choosing a new database character set ( NLS_CHARACTERSET )
 C) Changing the database character set in 8i, 9i, 10g and 11g.
 C1) Oracle RDBMS character set conversion for Oracle Application (EBS) or PeopleSoft systems .
 C2) Using export/import (or Datapump in 10g and up) into an different/new database in 8i, 9i, 10g and 11g.
 C3) Using a combination of ALTER DATABASE CHARACTER SET (8i, 9i) / CSALTER (10g and 11g) and export/import.
 C4) Step by step guides to do a character set conversion to Unicode (UTF8/AL32UTF8) (including export/import) in 8i, 9i, 10g and 11g.
 C5) What about Physical / Logical Standby (Data Guard) databases?
 C6) how to change from AL32UTF8/UTF8 back to an other characterset?
 D) Character set conversion to Unicode (UTF8/AL32UTF8) in Oracle RDBMS 12c.
 E) Character set restrictions with 12c Multitenant Container Databases (CDB) and Pluggable Databases (PDB) :
 F) Further reading

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