當我們手動copy了整個數據庫，並通過重建控制文件給數據庫指定了新的dbname，但是卻不能給數據庫分配新的dbid.對於以上問題我們可以通過nid命令來對數據庫分配一個全新的dbid。同時需要注意rman也是通過dbid來區分數據庫。
一 命令解釋
[oracle@source ~]$ nid help=yes
DBNEWID: Release 11.2.0.2.0 - Production on Thu Dec 5 00:09:50 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
Keyword Description (Default)
----------------------------------------------------
TARGET Username/Password (NONE) 指定連接數據庫的用戶名和密碼
DBNAME New database name (NONE) DBNAME=new_db_name 改變數據庫的名字
LOGFILE Output Log (NONE) LOGFILE=logfile指定輸出消息到指定的日誌文件，默認nid覆蓋之前的日子文件
REVERT Revert failed change NO 指定yes表明更改dbid失敗時能夠恢復之前的狀態
SETNAME Set a new database name only NO 指定yes表明僅僅更改數據庫db_name
APPEND Append to output log NO 指定yes標識輸出追加到已經存在的日誌文件
HELP Displays these messages NO 指定yes顯示幫助信息
注意：可以同時更改數據庫的dbid和db_name，也可以僅改變數據庫的db_name、抑或僅更改數據庫的dbid。語法分別如下：
改變dbid和db_name : nid target=sys/dhhzdhhz dbname=crm_test （也可以target=/）
僅改變db_name: nid target=sys/dhhzdhhz dbname=crm_test setname=yes （也可以target=/）
僅更改dbid： nid target=sys/dhhzdhhz （也可以target=/）
二 使用nid的注意事項
1 確保有能夠對數據庫進行完全恢復的備份。
2 確保執行更改dbid操作時數據庫處於mounted狀態且mounted之前數據庫是經過shutdown immediate關閉的。
3 使用nid更改數據庫的dbid後，數據庫需要alter database open resetlogs啓動，啓動之後須對數據庫進行一次全備份，因爲之前的備份和歸檔已經不能再使用了。
4 使用nid更改數據庫dbname後，需更改初始化參數文件中的DB_NAME參數並重建密碼文件。
5 使用nid不能更改全局數據庫名。
6 確保所有數據文件處於online狀態且不需要恢復。
7 儘量確保oracle沒有離線的數據文件和只讀表空間，如果有使其正常化。
三 舉兩個例子
eg1：僅更改數據庫dbid
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 1252663296 bytes
Fixed Size 2226072 bytes
Variable Size 922749032 bytes
Database Buffers 318767104 bytes
Redo Buffers 8921088 bytes
Database mounted.
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@source ~]$ nid target=sys
DBNEWID: Release 11.2.0.2.0 - Production on Wed Dec 4 23:39:11 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
Password:
Connected to database CRM (DBID=3599153036)
Connected to server version 11.2.0
Control Files in database:
/oracle/CRM/control03.ctl
Change database ID of database CRM? (Y/[N]) => y
Proceeding with operation
Changing database ID from 3599153036 to 3641774948
Control File /oracle/CRM/control03.ctl - modified
Datafile /oracle/CRM/system01.db - dbid changed
Datafile /oracle/CRM/sysaux01.db - dbid changed
Datafile /oracle/CRM/zx.db - dbid changed
Datafile /oracle/CRM/users01.db - dbid changed
Datafile /oracle/CRM/pos.db - dbid changed
Datafile /oracle/CRM/erp.db - dbid changed
Datafile /oracle/CRM/user01.db - dbid changed
Datafile /oracle/CRM/undotbs03.db - dbid changed
Datafile /oracle/CRM/crm.db - dbid changed
Datafile /oracle/CRM/jxc.db - dbid changed
Datafile /oracle/CRM/temp01.db - dbid changed
Control File /oracle/CRM/control03.ctl - dbid changed
Instance shut down
Database ID for database CRM changed to 3641774948.
All previous backups and archived redo logs for this database are unusable.
Database has been shutdown, open database with RESETLOGS option.
Succesfully changed database ID.
DBNEWID - Completed succesfully.
[oracle@source ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.2.0 Production on Wed Dec 4 23:47:21 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 1252663296 bytes
Fixed Size 2226072 bytes
Variable Size 922749032 bytes
Database Buffers 318767104 bytes
Redo Buffers 8921088 bytes
Database mounted.
SQL> alter database open resetlogs;
Database altered.
SQL> select dbid,name from v$database;
DBID NAME
---------- ---------
3641774948 CRM
eg2 ：僅更改數據庫db_name
oracle@source ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.2.0 Production on Thu Dec 5 00:11:03 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ WRITE
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 1252663296 bytes
Fixed Size 2226072 bytes
Variable Size 905971816 bytes
Database Buffers 335544320 bytes
Redo Buffers 8921088 bytes
Database mounted.
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
oracle@source ~]$ nid target=sys dbname=CRM_TEST setname=YES
DBNEWID: Release 11.2.0.2.0 - Production on Thu Dec 5 00:24:58 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
Password:
Connected to database CRM (DBID=3641774948)
Connected to server version 11.2.0
Control Files in database:
/oracle/CRM/control03.ctl
Change database name of database CRM to CRM_TEST? (Y/[N]) => y
Proceeding with operation
Changing database name from CRM to CRM_TEST
Control File /oracle/CRM/control03.ctl - modified
Datafile /oracle/CRM/system01.db - wrote new name
Datafile /oracle/CRM/sysaux01.db - wrote new name
Datafile /oracle/CRM/zx.db - wrote new name
Datafile /oracle/CRM/users01.db - wrote new name
Datafile /oracle/CRM/pos.db - wrote new name
Datafile /oracle/CRM/erp.db - wrote new name
Datafile /oracle/CRM/user01.db - wrote new name
Datafile /oracle/CRM/undotbs03.db - wrote new name
Datafile /oracle/CRM/crm.db - wrote new name
Datafile /oracle/CRM/jxc.db - wrote new name
Datafile /oracle/CRM/temp01.db - wrote new name
Control File /oracle/CRM/control03.ctl - wrote new name
Instance shut down
Database name changed to CRM_TEST.
Modify parameter file and generate a new password file before restarting.
Succesfully changed database name.
DBNEWID - Completed succesfully.
[oracle@source ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.2.0 Production on Thu Dec 5 00:25:33 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 1252663296 bytes
Fixed Size 2226072 bytes
Variable Size 905971816 bytes
Database Buffers 335544320 bytes
Redo Buffers 8921088 bytes
SQL> alter system set db_name=CRM_TEST scope=spfile;
System altered.
[oracle@source ~]$orapwd file="$ORACLE_HOME/dbs/orapw$ORACLE_SID" password=dhhzdhhz force=y
[oracle@source dbs]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.2.0 Production on Thu Dec 5 00:34:40 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> startup force open;
ORACLE instance started.
Total System Global Area 1252663296 bytes
Fixed Size 2226072 bytes
Variable Size 905971816 bytes
Database Buffers 335544320 bytes
Redo Buffers 8921088 bytes
Database mounted.
Database opened.
SQL> select dbid,name from v$database;
DBID NAME
---------- ---------
3641774948 CRM_TEST