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今天一朋友和我说他的数据库不能open,open过程提示ORA-00900错误,通过分析alert日志和props$表,发现他们修改了一个无效的NLS_CHARACTERSET值，导致数据库无法正常启动(准确的说，因为数据库里面该值无效，当数据库open的过程中，检测到控制文件指定的编码和该值不一致，然后修改控制文件的编码，修改之后，数据库一到mount状态执行任何语句都报ORA-00900错误),通过一些工具修改NLS_CHARACTERSET为正确值该故障解决
重现ORA-00900故障
代码如下 SQL> select * from v$version;BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
PL/SQL Release 11.2.0.3.0 - Production
CORE 11.2.0.3.0 Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
SQL> select value$ from props$ where name="NLS_CHARACTERSET";
VALUE$
-------------------------------------------------------
ZHS16GBK
SQL> update props$ set value$="AL16UTF16" where name="NLS_CHARACTERSET";
1 row updated.
SQL> commit;
Commit complete.
SQL> alter database backup controlfile to trace as "/tmp/ora11g.ctl";
Database altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 175775744 bytes
Fixed Size 1343668 bytes
Variable Size 117444428 bytes
Database Buffers 50331648 bytes
Redo Buffers 6656000 bytes
Database mounted.
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-00604: error occurred at recursive SQL level 1
ORA-00900: invalid SQL statement
Process ID: 5277
Session ID: 125 Serial number: 5
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 175775744 bytes
Fixed Size 1343668 bytes
Variable Size 117444428 bytes
Database Buffers 50331648 bytes
Redo Buffers 6656000 bytes
SQL> alter database mount;
Database altered.
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-00900: invalid SQL statement
SQL>select * from dual;
select * from dual
*
ERROR at line 1:
ORA-00900: invalid SQL statement
SQL> shutdown abort
ORACLE instance shut down.
第一次startup(open)过程报错
代码如下 SMON: enabling tx recoveryUpdating character set in controlfile to AL16UTF16
Errors in file /u01/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_5277.trc:
ORA-00604: error occurred at recursive SQL level %s
ORA-00900: invalid SQL statementursive SQL level %s
Errors in file /u01/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_5277.trc:
ORA-00604: error occurred at recursive SQL level %s
ORA-00900: invalid SQL statementursive SQL level %s
Error 604 happened during db open, shutting down database
USER (ospid: 5277): terminating the instance due to error 604
Errors in file /u01/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_smon_5243.trc:
ORA-00604: error occurred at recursive SQL level %s
ORA-00900: invalid SQL statementursive SQL level %s
Instance terminated by USER, pid = 5277
ORA-1092 signalled during: ALTER DATABASE OPEN...
opiodr aborting process unknown ospid (5277) as a result of ORA-1092
Sat May 18 00:44:27 2013
ORA-1092 : opitsk aborting process
这里比较明显的看到有一条(Updating character set in controlfile to AL16UTF16),正是由于这个操作，更新控制文件的编码为一个无效的编码，从而导致在后面数据库mount(加载控制文件)之后，就不能再进行其他任何操作
解决思路
使用odu找出来block位置，或者在同版本库中查询
使用dul或者bbed修改props$的NLS_CHARACTERSET值
重建控制文件(noresetlogs方式)
处理过程
代码如下 SQL> shutdown abortORACLE instance shut down.
odu找出来block位置
dul或者bbed修改block值
重建控制文件(noresetlogs方式)
ORACLE instance started.
Total System Global Area 175775744 bytes
Fixed Size 1343668 bytes
Variable Size 117444428 bytes
Database Buffers 50331648 bytes
Redo Buffers 6656000 bytes
Database mounted.
ORA-01113: file 1 needs media recovery
ORA-01110: data file 1: "/u01/oracle/oradata/ora11g/system01.dbf"
SQL> recover database;
Media recovery complete.
SQL> alter database open;
Database altered.
从oracle 9i开始，修改数据库的编码，直接使用alter database character set internal_use方式进行,而不要使用直接修改props$基表,更不能修改一个实际中不存在的编码值(本文中数据库编码和国家编码搞混淆从而出现该故障)