1.查詢v$database獲得

由于DBID在控制文件和數據文件中都存在記錄,所以如果能夠mount數據庫就可以查詢v$database視圖獲得.

復制代碼 代碼如下:

SQL> alter database mount;
Database altered.
SQL> select dbid from v$database;
      DBID
----------
3152029224

2.在nomount狀態時

如果數據庫配置了自動控制文件備份(Oracle9i),并且名稱是缺省的,那么我們可以從自動備份文件獲得DBID.

復制代碼 代碼如下:

[oracle@jumper dbs]$ cd $ORACLE_HOME/dbs
[oracle@jumper dbs]$ ll c-*
-rw-r----- 1 oracle dba 3375104 Dec 21 11:13 c-3152029224-20051221-00
-rw-r----- 1 oracle dba 3358720 Jan 21 14:03 c-3152029224-20060121-00
-rw-r----- 1 oracle dba 3358720 Jan 21 14:08 c-3152029224-20060121-01

這里的3152029224就是DBID。在10g中，使用Flash Recovery Area，則沒有這個命名規則。

3.從自動備份中恢復

需要或缺DBID進行恢復通常是因為丟失了所有的控制文件.在恢復時會遇到錯誤.

復制代碼 代碼如下:

[oracle@jumper dbs]$ rman target  /

Recovery Manager: Release 9.2.0.4.0 - Production

Copyright (c) 1995, 2002, Oracle Corporation.  All rights reserved.

connected to target database: conner (not mounted)

RMAN> restore controlfile from autobackup;

Starting restore at 05-FEB-06

using target database controlfile instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=11 devtype=DISK
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 02/05/2006 20:47:25
RMAN-06495: must explicitly specify DBID with SET DBID command

如果存在自動備份,我們通常可以直接恢復控制文件,mount數據庫之后就好辦了:

復制代碼 代碼如下:

RMAN> restore controlfile from '/opt/oracle/product/9.2.0/dbs/c-3152029224-20051221-00';

Starting restore at 05-FEB-06

using channel ORA_DISK_1
channel ORA_DISK_1: restoring controlfile
channel ORA_DISK_1: restore complete
replicating controlfile
input filename=/opt/oracle/oradata/conner/control01.ctl
output filename=/opt/oracle/oradata/conner/control02.ctl
output filename=/opt/oracle/oradata/conner/control03.ctl
Finished restore at 05-FEB-06

4.直接從幸存的文件中讀取

由于DBID存在于數據文件及控制文件中,所以我們可以通過PL/SQL程序直接從文件中讀取:

復制代碼 代碼如下:

SQL> select eygle.get_dbid('/opt/oracle/oradata/conner','user02.dbf') from dual;

EYGLE.GET_DBID('/OPT/ORACLE/OR
------------------------------
3152029224
SQL> select dbid from v$database;
DBID
----------
3152029224

其實更簡單的，用BBED就好了。

這種方法僅為測試興趣所致,不被推薦.