Need to change character set from WE8MSWIN1252 to AL32UTF8.

Hi,
We have installed the database with Character set WE8MSWIN1252. But off late we understood that client requirement is AL32UTF8. Is there any way to change in easy method?
Thanks in-advance.
Rgds
DBA.

Pl also see these Docs
AL32UTF8 / UTF8 (Unicode) Database Character Set Implications          [Document 788156.1]
Changing the NLS_CHARACTERSET to AL32UTF8 / UTF8 (Unicode)          [Document 260192.1]
If you are using EBS, then also see
For 11i - Appendix A of "Oracle Applications 11i Internationalization Guide          [Document 333785.1]"
For R12 - Appendix A of "Globalization Guide for Oracle Applications Release 12          [Document 393861.1]"
Changing the characterset of an existing database/application is not a trivial task - will require thorough planning and testing.
HTH
Srini

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    Article from Metalink
    Doc ID:      Note:66320.1
    Subject:      Changing the Database Character Set or the Database National Character Set
    Type:      BULLETIN
    Status:      PUBLISHED
         Content Type:      TEXT/PLAIN
    Creation Date:      23-OCT-1998
    Last Revision Date:      12-DEC-2003
    PURPOSE ======= To explain how to change the database character set or national character set of an existing Oracle8(i) or Oracle9i database without having to recreate the database. 1. SCOPE & APPLICATION ====================== The method described here is documented in the Oracle 8.1.x and Oracle9i documentation. It is not documented but it can be used in version 8.0.x. It does not work in Oracle7. The database character set is the character set of CHAR, VARCHAR2, LONG, and CLOB data stored in the database columns, and of SQL and PL/SQL text stored in the Data Dictionary. The national character set is the character set of NCHAR, NVARCHAR2, and NCLOB data. In certain database configurations the CLOB and NCLOB data are stored in the fixed-width Unicode encoding UCS-2. If you are using CLOB or NCLOB please make sure you read section "4. HANDLING CLOB AND NCLOB COLUMNS" below in this document. 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Oracle Support Services may pass the necessary information to customers after verifying the safety of the change for the customers' environments. If in Oracle9i an ALTER DATABASE NATIONAL CHARACTER SET is issued and there are N-type colums who contain data then this error is returned: ORA-12717:Cannot ALTER DATABASE NATIONAL CHARACTER SET when NCLOB data exists The error only speaks about Nclob but Nchar and Nvarchar2 are also checked see [NOTE:2310895.9] for bug [BUG:2310895] 4. HANDLING CLOB AND NCLOB COLUMNS ================================== Background ---------- In a fixed width character set codes of all characters have the same number of bytes. Fixed width character sets are: all single-byte character sets and those multibyte character sets which have names ending with 'FIXED'. In Oracle9i the character set AL16UTF16 is also fixed width. In a varying width character set codes of different characters may have different number of bytes. All multibyte character sets except those with names ending with FIXED (and except Oracle9i AL16UTF16 character set) are varying width. Single-byte character sets are character sets with names of the form xxx7yyyyyy and xxx8yyyyyy. Each character code of a single-byte character set occupies exactly one byte. Multibyte character sets are all other character sets (including UTF8). Some -- usually most -- character codes of a multibyte character set occupy more than one byte. CLOB values in a database whose database character set is fixed width are stored in this character set. CLOB values in an Oracle 8.0.x database whose database character set is varying width are not allowed. They have to be NULL. CLOB values in an Oracle >= 8.1.5 database whose database character set is varying width are stored in the fixed width Unicode UCS-2 encoding. The same holds for NCLOB values and the national character set. The UCS-2 storage format of character LOB values, as implemented in Oracle8i, ensures that calculation of character positions in LOB values is fast. Finding the byte offset of a character stored in a varying width character set would require reading the whole LOB value up to this character (possibly 4GB). In the fixed width character sets the byte offsets are simply character offsets multiplied by the number of bytes in a character code. In UCS-2 byte offsets are simply twice the character offsets. As the Unicode character set contains all characters defined in any other Oracle character set, there is no data loss when a CLOB/NCLOB value is converted to UCS-2 from the character set in which it was provided by a client program (usually the NLS_LANG character set). CLOB Values and the Database Character Set Change ------------------------------------------------- In Oracle 8.0.x CLOB values are invalid in varying width character sets. Thus you must delete all CLOB column values before changing the database character set to a varying width character set. In Oracle 8.1.5 and later CLOB values are valid in varying width character sets but they are converted to Unicode UCS-2 before being stored. But UCS-2 encoding is not a binary superset of any other Oracle character set. Even codes of the basic ASCII characters are different, e.g. single-byte code for "A"=0x41 becomes two-byte code 0x0041. This implies that even if the new varying width character set is a binary superset of the old fixed width character set and thus VARCHAR2/LONG character codes remain valid, the fixed width character codes in CLOB values will not longer be valid in UCS-2. As mentioned above, the ALTER DATABASE [NATIONAL] CHARACTER SET statement does not change character codes. Thus, before changing a fixed width database character set to a varying width character set (like UTF8) in Oracle 8.1.5 or later, you first have to export all tables containing non-NULL CLOB columns, then truncate these tables, then change the database character set and, finally, import the tables back to the database. The import step will perform the required conversion. If you omit the steps above, the character set change will succeed in Oracle8(i) (Oracle9i disallows the change in such situation) and the CLOBs may appear to be correctly legible but as their encoding is incorrect, they will cause problems in further operations. For example, CREATE TABLE AS SELECT will not correctly copy such CLOB columns. Also, after installation of the 8.1.7.3 server patchset the CLOB columns will not longer be legible. LONG columns are always stored in the database character set and thus they behave like CHAR/VARCHAR2 in respect to the character set change. BLOBs and BFILEs are binary raw datatypes and their processing does not depend on any Oracle character set setting. NCLOB Values and the National Character Set Change -------------------------------------------------- The above discussion about changing the database character set and exporting and importing CLOB values is theoretically applicable to the change of the national character set and to NCLOB values. But as varying width character sets are not supported as national character sets in Oracle8(i), changing the national character set from a fixed width character set to a varying width character set is not supported at all. Preparing CLOB Columns for the Character Set Change --------------------------------------------------- Take a backup of the database. If using Advanced Replication or deferred transactions functionality, make sure that there are no outstanding deferred transactions with CLOB parameters, i.e. DEFLOB view must have no rows with non-NULL CLOB_COL column; to make sure that replication environment remains consistent use only recommended methods of purging deferred transaction queue, preferably quiescing the replication environment. Then: - If changing the database character set from a fixed width character set to a varying with character set in Oracle 8.0.x, set all CLOB column values to NULL -- you are not allowed to use CLOB columns after the character set change. - If changing the database character set from a fixed width character set to a varying width character set in Oracle 8.1.5 or later, perform table-level export of all tables containing CLOB columns, including SYSTEM's tables. Set NLS_LANG to the old database character set for the Export utility. Then truncate these tables. Restoring CLOB Columns after the Character Set Change ----------------------------------------------------- In Oracle 8.1.5 or later, after changing the character set as described above (steps 3. to 6.), restore CLOB columns exported in step 2. by importing them back into the database. Set NLS_LANG to the old database character set for the Import utility to avoid IMP-16 errors and data loss. RELATED DOCUMENTS: ================== [NOTE:13856.1] V7: Changing the Database Character Set -- This note has limited distribution, please contact Oracle Support [NOTE:62107.1] The National Character Set in Oracle8 [NOTE:119164.1] Changing Database Character set - Valid Superset definitions [NOTE:118242.1] ALERT: Changing the Database or National Character Set Can Corrupt LOB Values <Note.158577.1> NLS_LANG Explained (How Does Client-Server Character Conversion Work?) [NOTE:140014.1] ALERT: Oracle8/8i to Oracle9i using New "AL16UTF16" [NOTE:159657.1] Complete Upgrade Checklist for Manual Upgrades from 8.X / 9.0.1 to Oracle9i (incl. 9.2) [NOTE:124721.1] Migrating an Applications Installation to a New Character Set Oracle8i National Language Support Guide Oracle8i Release 3 (8.1.7) Readme - Section 18.12 "Restricted ALTER DATABASE CHARACTER SET Command Support (CLOB and NCLOB)" Oracle8i Documentation Addendum, Release 3 (8.1.7) - Chapter 3 "New Character Set Scanner Utility" Oracle8i Application Developer's Guide - Large Objects (LOBs), Release 2 - Chapter 2 "Basic Components" Oracle8 Application Developer's Guide, Release 8.0 - Chapter 6 "Large Objects (LOBs)", Section "Introduction to LOBs" Oracle9i Globalization Guide, Release 1 (9.0.1) Oracle9i Database Globalization Guide, Release 2 (9.2) For further NLS / Globalization information you may start here: [NOTE:150091.1] Globalization Technology (NLS) Library index .
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    Joel P�rez

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