[20170120]db_unique_name与大小写.txt

--链接:http://www.itpub.net/thread-2083033-1-1.html,讨论db_unique_name大小写问题.实际上oracle到处是陷阱.
--通过例子说明:

1.环境:
SYS@book> @ &r/ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SYS@book> alter system set db_unique_name=book ;
alter system set db_unique_name=book
                 *
ERROR at line 1:
ORA-02095: specified initialization parameter cannot be modified

--这个参数仅仅修改spfile,重启才生效.

SYS@book> show parameter db_unique_name
NAME           TYPE   VALUE
-------------- ------ ------
db_unique_name string book
--//可以发现我设置是小写,缺省你不设置好像也是小写.

2.测试:
SYS@book> alter system set db_unique_name=book scope=spfile;
System altered.

$ strings spfilebook.ora| grep -i db_unique_name=
*.db_unique_name='BOOK'

--//可以发现现在是大写.

--//要设置小写,必须这样写引号.
SYS@book> alter system set db_unique_name='book' scope=spfile;
System altered.

$ strings spfilebook.ora| grep -i db_unique_name=
*.db_unique_name='book'

--//取消设置.
SYS@book> alter system reset db_unique_name;
System altered.

3.重启数据库:
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.

SYS@book> startup
ORACLE instance started.
Total System Global Area  634732544 bytes
Fixed Size                  2255792 bytes
Variable Size             197133392 bytes
Database Buffers          427819008 bytes
Redo Buffers                7524352 bytes
Database mounted.
Database opened.

SYS@book> show parameter db_unique_name
NAME           TYPE   VALUE
-------------- ------ ------
db_unique_name string book

--// 设置大写.重启数据库看看.
SYS@book> alter system set db_unique_name=book scope=spfile;
System altered.

SYS@book> show parameter db_unique_name
NAME           TYPE   VALUE
-------------- ------ -------
db_unique_name string BOOK

--//不过一些参数并没有这个改变而发生变化:

SYS@book> show parameter dump
NAME                 TYPE    VALUE
-------------------- ------- -------------------------------------------
background_core_dump string  partial
background_dump_dest string  /u01/app/oracle/diag/rdbms/book/book/trace
core_dump_dest       string  /u01/app/oracle/diag/rdbms/book/book/cdump
max_dump_file_size   string  unlimited
shadow_core_dump     string  partial
user_dump_dest       string  /u01/app/oracle/diag/rdbms/book/book/trace

--//我个人估计对dg应该也没有什么影响.
--//instance_name也是一样的效果,大家可以自己测试.