深入了解回滚表空间丢失的解决方法

问题：Oracle数据库的undotbs01.dbf文件损坏？
解决方法如下：
首先，我们需要模拟这个错误，方法是将undotbs01.dbf移到其它目录下，然后再来进行修正，过程如下：
SQL> startup
ORACLE instance started.
Total System Global Area  135338868 bytes
Fixed Size                   453492 bytes
Variable Size             109051904 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: ''D:\ORACLE\ORADATA\ORCL\UNDOTBS01.DBF''
SQL> alter system set undo_management=''MANUAL'' scope=spfile;
System altered.
SQL> alter database datafile ''d:\oracle\oradata\orcl\undotbs01.dbf'' offline drop;
Database altered.
SQL> alter database open;
Database altered.
SQL>
现在，此数据库已经能正常启动，但是还是没有达到我们的要求，因为在Oracle9i以后的版本建议用undo表空间来代替回滚段，现在我们需要将其设置为undo表空间。
SQL>
create undo tablespace undotbs2 datafile '
'd:\oracle\oradata\orcl\undotbs02.dbf'' size 100M;
Tablespace created.
SQL> select * from v$tablespace;

       TS# NAME                           INC
---------- ------------------------------ ---
         3 CWMLITE                        YES
         4 DRSYS                          YES
         5 EXAMPLE                        YES
         6 INDX                           YES
         7 ODM                            YES
         0 SYSTEM                         YES
         8 TOOLS                          YES
         1 UNDOTBS1                       YES
         9 USERS                          YES
        10 XDB                            YES
         2 TEMP                           YES

       TS# NAME                           INC
---------- ------------------------------ ---
        11 UNDOTBS2                       YES

12 rows selected.

SQL> alter system set undo_management=''AUTO'' scope=spfile;

System altered.

SQL> alter system set undo_tablespace=''UNDOTBS2'' scope=spfile;

System altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area  135338868 bytes
Fixed Size                   453492 bytes
Variable Size             109051904 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database mounted.
Database opened.
SQL> show parameter undo

NAME                                 TYPE        VALUE
------------------------------------ ----------- -----
undo_management                      string      AUTO
undo_retention                       integer     10800
undo_suppress_errors                 boolean     FALSE
undo_tablespace                      string      UNDOTBS2
SQL>
此时，数据库成功启动。