$ export ORACLE_SID=cfgdb

SQL> startup nomount;

SQL> alter system reset control_files scope=spfile sid='*';
SQL> startup force nomount;

$ rman target sys/sys@devcfgdb  auxiliary /

RMAN> DUPLICATE TARGET DATABASE TO CFGDB;

删除表空间恢复

1:数据库在归档模式下运行，没有任何备份能恢复吗?
答:你有该表空间创建以来的所有归档日志,重新新建一个,否则没有办法。

2:在非归档模式下运行，能恢复吗?

SQL>create table wt_tb tablespace wt as select * from dba_objects;
SQL>alter database backup controlfile to trace;

RMAN> backup database;

SQL>alter database backup controlfile to trace;
SQL>drop tablespace wt including contents;

SQL>shutdown immediate;
SQL>startup;

要恢复被删除的表空间，一定要满足如下条件:
1:控制文件里有这些信息，我们上面已经做了;
2:数据字典里也要有相关信息，那么我们必须恢复system表空间，到未删除之前的状态;

#rm system01.dbf

SQL>startup mount;

RMAN> connect target
RMAN> restore datafile 1;

SQL>shutdown immediate;
SQL>startup nomount;
SQL>CREATE CONTROLFILE REUSE DATABASE "WTDB" RESETLOGS ARCHIVELOG

          ....................................;

SQL>select name,checkpoint_time from v$datafile;
NAME
-------------------------------------------------------------------------------------------------------
-----------------------------------------------
CHECKPOINT_TIME
-------------------
/disk2/oradata/wtdb/system01.dbf
2008-09-02 09:11:57
/disk2/oradata/wtdb/undotbs01.dbf
2008-09-02 09:13:10
/disk2/oradata/wtdb/donny.dbf
2008-09-02 09:13:10
/disk2/oradata/wtdb/wtdb01.dbf
2008-09-02 09:12:57

SQL>alter database open resetlogs;

SQL>select name,checkpoint_time from v$datafile;
NAME
-------------------------------------------------------------------------------------------------------
-----------------------------------------------
CHECKPOINT_TIME
-------------------
/disk2/oradata/wtdb/system01.dbf
2008-09-02 09:25:16
/disk2/oradata/wtdb/undotbs01.dbf
2008-09-02 09:25:16/disk2/oradata/wtdb/donny.dbf
2008-09-02 09:25:16
/disk2/oradata/wtdb/wtdb01.dbf
2008-09-02 09:25:16

SQL>select count(*) from wt_tb;
COUNT(*)
----------
6164