未提交事务屏蔽回滚段

1、插入数据

SQL> select count(*) from t1;

  COUNT(*)
----------
      9156
SQL> insert into t1 select * from t1;

9156 rows created.

SQL> select count(*) from t1;

  COUNT(*)
----------
     18312

SQL> shutdown abort
ORACLE instance shut down.

2、删除undo

[oracle@target target]$ rm -rf undotbs01.dbf 

3、启动数据库报错

SQL> startup
ORACLE instance started.

Total System Global Area  839282688 bytes
Fixed Size                  2257880 bytes
Variable Size             545262632 bytes
Database Buffers          289406976 bytes
Redo Buffers                2355200 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/u01/app/oracle/oradata/target/undotbs01.dbf'

4、将undo offline

SQL> alter database datafile '/u01/app/oracle/oradata/target/undotbs01.dbf' offline drop;

Database altered.

5、开启数据库

SQL>  alter database open

6、查询表报错

SQL> select count(*) from test1.t1;
select count(*) from test1.t1
                           *
ERROR at line 1:
ORA-00376: file 3 cannot be read at this time
ORA-01110: data file 3: '/u01/app/oracle/oradata/target/undotbs01.dbf'

7、重新创建undo1

SQL>  create undo tablespace undo1 datafile '/u01/app/oracle/oradata/target/undo1.dbf' size 100m;

Tablespace created.

SQL> show parameter undo

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     900
undo_tablespace                      string      UNDOTBS1
SQL> alter system set undo_tablespace='UNDO1';

System altered.

SQL> show parameter undo

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     900
undo_tablespace                      string      UNDO1

7、查询报错，查询回滚段

SQL>  select count(*) from test1.t1;
 select count(*) from test1.t1
                            *
ERROR at line 1:
ORA-00376: file 3 cannot be read at this time
ORA-01110: data file 3: '/u01/app/oracle/oradata/target/undotbs01.dbf'

SQL> select segment_name,status from dba_rollback_segs;

SEGMENT_NAME                   STATUS
------------------------------ ----------------
SYSTEM                         ONLINE
_SYSSMU10_1197734989$          NEEDS RECOVERY
_SYSSMU9_1650507775$           NEEDS RECOVERY
_SYSSMU8_517538920$            NEEDS RECOVERY
_SYSSMU7_2070203016$           NEEDS RECOVERY
_SYSSMU6_1263032392$           NEEDS RECOVERY
_SYSSMU5_898567397$            NEEDS RECOVERY
_SYSSMU4_1254879796$           NEEDS RECOVERY
_SYSSMU3_1723003836$           NEEDS RECOVERY
_SYSSMU2_2996391332$           NEEDS RECOVERY
_SYSSMU1_3724004606$           NEEDS RECOVERY

SEGMENT_NAME                   STATUS
------------------------------ ----------------
_SYSSMU20_1207334500$          ONLINE
_SYSSMU19_1240195038$          ONLINE
_SYSSMU18_1271537130$          ONLINE
_SYSSMU17_3251087833$          ONLINE
_SYSSMU16_2848467477$          ONLINE
_SYSSMU15_2454094217$          ONLINE
_SYSSMU14_1072233045$          ONLINE
_SYSSMU13_2051731998$          ONLINE
_SYSSMU12_1292947808$          ONLINE
_SYSSMU11_1337237917$          ONLINE

21 rows selected.

8、spfile中写入

_offline_rollback_segments=(_SYSSMU10_1197734989$,_SYSSMU9_1650507775$,_SYSSMU8_517538920$,_SYSSMU7_2070203016$,_SYSSMU6_1263032392$ ,_SYSSMU5_898567397$,_SYSSMU4_1254879796$,_SYSSMU3_1723003836$,_SYSSMU2_2996391332$,_SYSSMU1_3724004606$)
_corrupted_rollback_segments=(_SYSSMU10_1197734989$,_SYSSMU9_1650507775$,_SYSSMU8_517538920$,_SYSSMU7_2070203016$,_SYSSMU6_1263032392$ ,_SYSSMU5_898567397$,_SYSSMU4_1254879796$,_SYSSMU3_1723003836$,_SYSSMU2_2996391332$,_SYSSMU1_3724004606$)

9、重新生成spfile

SQL> startup nomount pfile='/tmp/pfile';
ORACLE instance started.

Total System Global Area  839282688 bytes
Fixed Size                  2257880 bytes
Variable Size             545262632 bytes
Database Buffers          289406976 bytes
Redo Buffers                2355200 bytes

SQL> create spfile from pfile='/tmp/pfile';

File created.

SQL> shutdown abort
ORACLE instance shut down.

10、启动数据库t1表可以查询到结果

SQL> startup
ORACLE instance started.

Total System Global Area  839282688 bytes
Fixed Size                  2257880 bytes
Variable Size             545262632 bytes
Database Buffers          289406976 bytes
Redo Buffers                2355200 bytes
Database mounted.
Database opened.
SQL> 
SQL> 
SQL> select count(*) from test1.t1;

  COUNT(*)
----------
     18312