在向大家详细介绍CentOS Data Guard 之前，首先让大家了解下CentOS Data Guard ，然后全面介绍CentOS Data Guard ，希望对大家有用。[实验]CentOS Data Guard环境下修改数据库字符集 环境.

VMWARE  
OS：CentOS 5.3  
Primary：Oracle 10.2.0.1.0  
Standby：Oracle 10.2.0.1.0 

CentOS Data Guard下面的操作均在Primary上，不会影响到Standby DB，备库需要单独操作。数据库更改字符集：源字符集CentOS Data Guard目标字符集WE8ISO8859P1 --> AL32UTF8AL16UTF16 --> AL16UTF16

<方法一>：由于目标CentOS Data Guard字符集不是源字符集的超集，所以导致失败

　　Startup nomount;  
　　Alter database mount exclusive;  
　　Alter system enable restricted session;  
　　Alter system set job_queue_processes=0;**  
　　Alter database open;  
　　Alter database character set AL32UTF8; 

在***一步报错，内容为目标字符集不是源字符集的超集过程：

SQL> shutdown immediate;  
Database closed.  
Database dismounted.  
ORACLE instance shut down.  
SQL> startup nomount;  
ORA-32004: obsolete and/or deprecated parameter(s) specified  
ORACLE instance started.  

Total System Global Area  272629760 bytes  
Fixed Size                  1218920 bytes  
Variable Size              92276376 bytes  
Database Buffers          176160768 bytes  
Redo Buffers                2973696 bytes  
SQL> Alter database mount exclusive;  

Database altered.  
SQL> Alter system enable restricted session;  
System altered.  
SQL> Alter system set job_queue_processes=0;  
System altered.  
SQL> Alter database open;  
Database altered.  
SQL> Alter database character set AL32UTF8;  
Alter database character set AL32UTF8  
ERROR at line 1:  
ORA-12712: new character set must be a superset of old character set  

SQL> host  
[oracle@Primary ~]$ oerr ora 12712  
12712, 00000, "new character set must be a superset of old character set"  
// *Cause: When you ALTER DATABASE ... CHARACTER SET, the new  
//         character set must be a superset of the old character set.  
//         For example, WE8ISO8859P1 is not a superset of the WE8DEC.  
// *Action: Specify a superset character set.  

 CentOS Data Guard<方法二>：成功，但此方法非常危险，可能会造成数据库崩溃
SQL> show user;
USER is "SYS"
SQL> select status from v$instance; 
STATUS
OPEN
SQL> update props$ set value$ = 'AL32UTF8' where name = 'NLS_CHARACTERSET';
 
1 row updated.SQL> update props$ set value$ = 'AL16UTF16' where name = 'NLS_NCHAR_CHARACTERSET';1 row updated.SQL> commit;Commit complete.
 
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
/home/oracle>sqlplus / as sysdba;
 
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Apr 15 17:15:47 2009
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
 
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORA-32004: obsolete and/or deprecated parameter(s) specified
ORACLE instance started.
 
Total System Global Area  272629760 bytes
Fixed Size                  1218920 bytes
Variable Size              92276376 bytes
Database Buffers          176160768 bytes
Redo Buffers                2973696 bytes
Database mounted.
SQL> alter system enable restricted session;
 
System altered.
 
SQL> alter system set job_queue_processes=0;
 
System altered.
 
SQL> alter database open;
 
Database altered.
 
SQL> alter database character set AL32UTF8;
 
Database altered.
 
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
/home/oracle>sqlplus / as sysdba;
 
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Apr 15 17:21:15 2009
 
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
 
Connected to an idle instance.
 
SQL> startup
ORA-32004: obsolete and/or deprecated parameter(s) specified
ORACLE instance started.
 
Total System Global Area  272629760 bytes
Fixed Size                  1218920 bytes
Variable Size              92276376 bytes
Database Buffers          176160768 bytes
Redo Buffers                2973696 bytes
Database mounted.
Database opened.
 
SQL>select * from v$nls_parameters;
1 NLS_LANGUAGE SIMPLIFIED CHINESE
2 NLS_TERRITORY CHINA
3 NLS_CURRENCY ？
4 NLS_ISO_CURRENCY CHINA
5 NLS_NUMERIC_CHARACTERS .,
6 NLS_CALENDAR GREGORIAN
7 NLS_DATE_FORMAT DD-MON-RR
8 NLS_DATE_LANGUAGE SIMPLIFIED CHINESE
9 NLS_CHARACTERSET WE8ISO8859P1
10 NLS_SORT BINARY
11 NLS_TIME_FORMAT HH.MI.SSXFF AM
12 NLS_TIMESTAMP_FORMAT DD-MON-RR HH.MI.SSXFF AM
13 NLS_TIME_TZ_FORMAT HH.MI.SSXFF AM TZR
14 NLS_TIMESTAMP_TZ_FORMAT DD-MON-RR HH.MI.SSXFF AM TZR
15 NLS_DUAL_CURRENCY ？
16 NLS_NCHAR_CHARACTERSET AL16UTF16
17 NLS_COMP BINARY
18 NLS_LENGTH_SEMANTICS BYTE
19 NLS_NCHAR_CONV_EXCP FALSE
CentOS Data Guard成功更改！

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