基于某些特定的需要我们需要改数据库名，下面是实验：
version:
Linux chartis 2.6.32-200.13.1.el5uek #1 SMP Wed Jul 27 21:02:33 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux
SQL*Plus: Release 11.2.0.1.0 Production on Mon Jan 7 16:23:04 2013
改名前：
SQL> show parameter name
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_file_name_convert string
db_name string gun2
db_unique_name string gun2
global_names boolean FALSE
instance_name string gun2
lock_name_space string
log_file_name_convert string
service_names string gun2
这个实验需要把这里的gun2改为gun，其中包括instance_name和db_name.
1,备份controlfile,提取创建controlfile的语句
SQL> alter database backup controlfile to trace;
Database altered.
SQL>
select c.value || '/' || d.instance_name || '_ora_' ||
to_char(a.spid,'fm99999') || '.trc'
from v$process a, v$session b, v$parameter c, v$instance d
where a.addr = b.paddr
and b.audsid = userenv('sessionid')
6 and c.name = 'user_dump_dest';
C.VALUE||'/'||D.INSTANCE_NAME||'_ORA_'||TO_CHAR(A.SPID,'FM99999')||'.TRC'
--------------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/gun2/gun2/trace/gun2_ora_6805.trc
创建控制文件的语句(当然要做一些修改，粗体部分要特别注意)：
CREATE CONTROLFILE set DATABASE "GUN" RESETLOGS NOARCHIVELOG
MAXLOGFILES 16
MAXLOGMEMBERS 3
MAXDATAFILES 100
MAXINSTANCES 8
MAXLOGHISTORY 292
LOGFILE
GROUP 1 '/u01/app/oracle/oradata/gun/redo01.log' SIZE 50M BLOCKSIZE 512,
GROUP 2 '/u01/app/oracle/oradata/gun/redo02.log' SIZE 50M BLOCKSIZE 512,
GROUP 3 '/u01/app/oracle/oradata/gun/redo03.log' SIZE 50M BLOCKSIZE 512
-- STANDBY LOGFILE
DATAFILE
'/u01/app/oracle/oradata/gun/system01.dbf',
'/u01/app/oracle/oradata/gun/sysaux01.dbf',
'/u01/app/oracle/oradata/gun/undotbs01.dbf',
'/u01/app/oracle/oradata/gun/users01.dbf',
'/u01/app/oracle/oradata/gun/ogg01.dbf',
'/u01/app/oracle/oradata/gun/mysys01.dbf',
'/u01/app/oracle/oradata/gun/mdu01.dbf'
CHARACTER SET ZHS16GBK
;
2,创建pfile文件并修改pfile
SQL> create pfile from spfile;
File created.
[oracle@chartis dbs]$ pwd
/u01/app/oracle/product/11.2.0/db_1/dbs
[oracle@chartis dbs]$ mv initgun2.ora initgun.ora
修改initgun.ora
将所有的gun2改为gun，并创建audit_file_dest,control_files参数指定的目录(不创建目录startup nomount时会报错)。
3,修改.bash_profile中的ORACLE_SID
ORACLE_SID=gun -----到这里，控制实例名的参数已经改完
4,拷贝原数据库/u01/app/oracle/oradata/gun2/中的datafile，redo log到/u01/app/oracle/oradata/gun/目录
注意不包括controlfile并且这里是关闭数据库的后复制。
拷贝之前要关闭原数据库
SQL>shutdown immediate
5,创建控制文件
[oracle@chartis ~]$ source .bash_profile
[oracle@chartis ~]$ env|grep ORA
ORACLE_SID=gun
ORACLE_BASE=/u01/app/oracle
ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
SQL> startup nomount
ORACLE instance started.
Total System Global Area 730714112 bytes
Fixed Size 2216944 bytes
Variable Size 566234128 bytes
Database Buffers 159383552 bytes
Redo Buffers 2879488 bytes
SQL>CREATE CONTROLFILE set DATABASE "GUN" RESETLOGS NOARCHIVELOG
MAXLOGFILES 16
MAXLOGMEMBERS 3
MAXDATAFILES 100
MAXINSTANCES 8
MAXLOGHISTORY 292
LOGFILE
GROUP 1 '/u01/app/oracle/oradata/gun/redo01.log' SIZE 50M BLOCKSIZE 512,
GROUP 2 '/u01/app/oracle/oradata/gun/redo02.log' SIZE 50M BLOCKSIZE 512,
GROUP 3 '/u01/app/oracle/oradata/gun/redo03.log' SIZE 50M BLOCKSIZE 512
DATAFILE
'/u01/app/oracle/oradata/gun/system01.dbf',
'/u01/app/oracle/oradata/gun/sysaux01.dbf',
'/u01/app/oracle/oradata/gun/undotbs01.dbf',
'/u01/app/oracle/oradata/gun/users01.dbf',
'/u01/app/oracle/oradata/gun/ogg01.dbf',
'/u01/app/oracle/oradata/gun/mysys01.dbf',
'/u01/app/oracle/oradata/gun/mdu01.dbf'
CHARACTER SET ZHS16GBK
;
Control file created.
SQL> alter database open resetlogs;
Database altered.
SQL> show parameter name
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_file_name_convert string
db_name string gun
db_unique_name string gun
global_names boolean FALSE
instance_name string gun
lock_name_space string
log_file_name_convert string
service_names string gun
全部已经改好了。
可进一步参考：http://blog.itpub.net/post/29894/481048