11.2.0.2裏新增了一個新特性——用戶重命名(Rename User)，在這個版本之前要想重命名用戶，需要按用戶導出，再fromuser touser（imp）或remap_schem（impdp）。還可以通過修改數據字典user$的方式來重命名用戶，但這種方法可能會帶來風險。有了這個特性之後，可以通過alter user oldname rename to newname identified by "password";一條命令來重命名用戶。
下面來看測試過程，使用Oracle版本11.2.0.4
sys@ORCL>select * from v$version; BANNER ------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production PL/SQL Release 11.2.0.4.0 - Production CORE 11.2.0.4.0 Production TNS for Linux: Version 11.2.0.4.0 - Production NLSRTL Version 11.2.0.4.0 - Production
1、創建測試用戶及測試表
sys@ORCL>create user sq identified by "sq"; User created. sys@ORCL>grant connect,resource to sq; Grant succeeded sys@ORCL>create table sq.t1 as select * from dba_tables; Table created.
2、執行alter user語句
sys@ORCL>alter user sq rename to zlx identified by "zlx"; alter user sq rename to zlx identified by "zlx" * ERROR at line 1: ORA-00922: missing or invalid option
報錯無效的操作，原來是需要修改隱含參數"_enable_rename_user"
3、修改隱含參數"_enable_rename_user"，並以restrict模式重啓數據庫
sys@ORCL>alter system set "_enable_rename_user"=true scope=spfile; System altered. sys@ORCL>startup restrict force; ORACLE instance started. Total System Global Area 1620115456 bytes Fixed Size 2253704 bytes Variable Size 956304504 bytes Database Buffers 654311424 bytes Redo Buffers 7245824 bytes Database mounted. Database opened.
4、再次執行alter user語句，重命名用戶
sys@ORCL>alter user sq rename to zlx identified by "zlx"; User altered. sys@ORCL>select count(*) from sq.t1; select count(*) from sq.t1 * ERROR at line 1: ORA-00942: table or view does not exist sys@ORCL>select count(*) from zlx.t1; COUNT(*) ---------- 2864 sys@ORCL>conn zlx/zlx ERROR: ORA-01035: ORACLE only available to users with RESTRICTED SESSION privilege Warning: You are no longer connected to ORACLE. sys@ORCL>conn / as sysdba Connected. sys@ORCL>alter system disable restricted session; System altered. sys@ORCL>conn zlx/zlx Connected. zlx@ORCL>select * from tab; TNAME TABTYPE CLUSTERID ------------------------------------------ --------------------- ---------- T1 TABLE
從上面的結果來看用戶名重命名成功。
5、reset隱含參數"_enable_rename_user"並重啓數據庫
sys@ORCL>alter system reset "_enable_rename_user";
System altered.
下面來看直接修改數據字典user$的方法：
sys@ORCL>select user#,name from user$ where name='ZLX';
USER# NAME
---------- --------
94 ZLX
sys@ORCL>update user$ set name='SQ' WHERE USER#=94;
1 row updated.
sys@ORCL>commit;
Commit complete.
sys@ORCL>conn sq/zlx;
Connected.
網上還提到update完後，需要alter system checkpoint;和alter system flush shared_pool;，從上面的操作來看好象更簡單一些，但user$作爲oracle的核心基表之一，修改數據字典會不會造成系統不穩定產生ora-600錯誤等等都不好說，所以生產上一定要慎重。