[20121009]global_name是什么.txt

[20121009]global_name是什么.txt

看看与学习global_names是什么在11GR2.

SQL> select * from v$version ;

BANNER

--------------------------------------------------------------------------------

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production

PL/SQL Release 11.2.0.1.0 - Production

CORE    11.2.0.1.0      Production

TNS for Linux: Version 11.2.0.1.0 - Production

NLSRTL Version 11.2.0.1.0 - Production

SQL> select * from global_name;

GLOBAL_NAME

-----------

TEST.COM

SQL> column object_name format a20

SQL> column owner format a20

SQL> SELECT owner, object_name, object_id, data_object_id, object_type FROM dba_objects WHERE object_name = 'GLOBAL_NAME';

OWNER                OBJECT_NAME           OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE

-------------------- -------------------- ---------- -------------- -------------------

SYS                  GLOBAL_NAME                3327                VIEW

PUBLIC               GLOBAL_NAME                3328                SYNONYM

--可以看出普通用户通过SYNONYM的GLOBAL_NAME访问.
--看看同义词的定义:

SQL> column db_link format a20

SQL> SELECT *  FROM dba_synonyms WHERE wner = 'PUBLIC' AND synonym_name = 'GLOBAL_NAME';

OWNER                          SYNONYM_NAME                   TABLE_OWNER                    TABLE_NAME                     DB_LINK

------------------------------ ------------------------------ ------------------------------ ------------------------------ --------------------

PUBLIC                         GLOBAL_NAME                    SYS                            GLOBAL_NAME

--推出通过同义词访问view,再看看view的定义:

SQL> column text format a60

SQL> SELECT owner,view_name,text_length,text  FROM dba_views WHERE wner = 'SYS' AND view_name = 'GLOBAL_NAME';

OWNER                          VIEW_NAME                      TEXT_LENGTH TEXT

------------------------------ ------------------------------ ----------- ------------------------------------------------------------

SYS                            GLOBAL_NAME                             59 select value$ from sys.props$ where name = 'GLOBAL_DB_NAME'

--可以看出最后访问的对象是select value$ from sys.props$ where name = 'GLOBAL_DB_NAME'.

SQL> select rowid x,a.* from sys.props$ a where name='GLOBAL_DB_NAME';

X                  NAME                 VALUE$                         COMMENT$

------------------ -------------------- ------------------------------ --------------------

AAAABiAABAAAAMhAAf GLOBAL_DB_NAME       TEST.COM                       Global database name

SQL> @ lookup_rowid.sql  AAAABiAABAAAAMhAAf

    OBJECT       FILE      BLOCK        ROW

---------- ---------- ---------- ----------

        98          1        801         31

---理解这些东西主要目的是为了下面bbed的学习做一些准备,因为在10g以上版本如果执行:

update global_name set global_name='';

commit;

下次开机时,出现如下提示:

SQL> startup

ORACLE instance started.

Total System Global Area 2137886720 bytes

Fixed Size                  2215064 bytes

Variable Size            1728054120 bytes

Database Buffers          402653184 bytes

Redo Buffers                4964352 bytes

Database mounted.

ORA-01092: ORACLE instance terminated. Disconnection forced

ORA-00600: internal error code, arguments: [18062], [], [], [], [], [], [], [], [], [], [], []

Process ID: 632

Session ID: 530 Serial number: 3

--许多blog都提到不能修改global_name为空.
最好使用

alter database rename global_name to xxxx.com;