今天在做数据迁移的时候发现磁盘空间完全被吃完，查看undo表空间竟然占了25G。这里记录重建undo表空间过程。

1、重建undo表空间undotbs2SQL> create undo tablespace undotbs2 datafile 'D:\ora11g\undotbs2_01.dbf' size 1G autoextend on next 500M maxsize unlimited;

表空间已创建。

2、修改undo_tablespace参数，该参数必须设置 SQL> alter system set undo_tablespace=undotbs2 scope=both;

系统已更改。

查看切换后的状态：SQL> show parameter undo_tablespace

UNDO_TABLESPACE---------------UNDOTBS2

3、查看原undo表空间UNDOTBS1各个undo段状态，当状态都为offline时则可以将该undo表空间删除 SQL> select segment_name,tablespace_name,status from dba_rollback_segs;

SEGMENT_NAME                   TABLESPACE_NAME                STATUS------------------------------ ------------------------------ ----------------SYSTEM                         SYSTEM                         ONLINE_SYSSMU19_1323384053$          UNDOTBS1                       OFFLINE_SYSSMU18_2053914518$          UNDOTBS1                       OFFLINE_SYSSMU17_1486782901$          UNDOTBS1                       OFFLINE_SYSSMU16_65961640$            UNDOTBS1                       OFFLINE_SYSSMU15_2731980009$          UNDOTBS1                       OFFLINE_SYSSMU14_1272261740$          UNDOTBS1                       OFFLINE_SYSSMU13_3931036527$          UNDOTBS1                       OFFLINE_SYSSMU12_277474270$           UNDOTBS1                       OFFLINE_SYSSMU11_1127233206$          UNDOTBS1                       OFFLINE_SYSSMU10_2010384090$          UNDOTBS1                       OFFLINE_SYSSMU9_3385418537$           UNDOTBS1                       OFFLINE_SYSSMU8_960788264$            UNDOTBS1                       OFFLINE_SYSSMU7_2218399740$           UNDOTBS1                       OFFLINE_SYSSMU6_4013851069$           UNDOTBS1                       OFFLINE_SYSSMU5_14816259$             UNDOTBS1                       OFFLINE_SYSSMU4_3531847310$           UNDOTBS1                       OFFLINE_SYSSMU3_3898657637$           UNDOTBS1                       ONLINE_SYSSMU2_2881644447$           UNDOTBS1                       OFFLINE_SYSSMU1_1093178884$           UNDOTBS1                       OFFLINE_SYSSMU43_2526432190$          UNDOTBS2                       ONLINE_SYSSMU42_1073097992$          UNDOTBS2                       ONLINE_SYSSMU41_4185790622$          UNDOTBS2                       ONLINE_SYSSMU40_4075868025$          UNDOTBS2                       ONLINE_SYSSMU39_1225046965$          UNDOTBS2                       ONLINE_SYSSMU38_1416928319$          UNDOTBS2                       ONLINE_SYSSMU37_425218863$           UNDOTBS2                       ONLINE_SYSSMU36_2283506252$          UNDOTBS2                       ONLINE_SYSSMU35_3741949710$          UNDOTBS2                       ONLINE_SYSSMU34_3108701464$          UNDOTBS2                       ONLINE_SYSSMU33_1440052939$          UNDOTBS2                       ONLINE_SYSSMU31_867868996$           UNDOTBS2                       ONLINE_SYSSMU30_4206031811$          UNDOTBS2                       ONLINE_SYSSMU29_1581029439$          UNDOTBS2                       ONLINE_SYSSMU28_2713846431$          UNDOTBS2                       ONLINE_SYSSMU27_2818503999$          UNDOTBS2                       ONLINE_SYSSMU26_3492104676$          UNDOTBS2                       ONLINE_SYSSMU25_231788078$           UNDOTBS2                       ONLINE_SYSSMU24_494800911$           UNDOTBS2                       ONLINE_SYSSMU23_3011088732$          UNDOTBS2                       ONLINE_SYSSMU22_358374592$           UNDOTBS2                       ONLINE_SYSSMU21_3370208409$          UNDOTBS2                       ONLINE

已选择42行。

这时看到回滚段_SYSSMU3_3898657637$依然处于online状态，需要等到状态变为offline时才可以drop掉表空间。

4、这时也可以查看下到底是哪个操作在占用该回滚段，如果不重要将该进程杀掉即可。SQL> show parameter undo_tablespace

NAME                                 TYPE        VALUE------------------------------------ ----------- ------------------------------undo_tablespace                      string      UNDOTBS2SQL> select r.name,  2         s.sid,  3         s.serial#,  4         s.username,  5         s.machine,  6         t.start_time,  7         t.status,  8         substr(s.program, 1, 15) operate  9    from v$session s, v$transaction t, v$rollname r, v$rollstat g 10   where t.addr = s.taddr 11     and t.xidusn = r.usn 12     and r.usn = g.usn and r.name='_SYSSMU3_3898657637$' 13   order by t.used_ublk desc;

NAME                                  SID    SERIAL#  USERNAME           MACHINE                  START_TIME           STATUS            OPERATE------------------------------ ---------- ----------  ---------------    ------------------------ --------------------- ---------------- ------------------_SYSSMU3_3898657637$                  131      24783  SJQY_1130          PDOMAIN\WIN-M8G18I89RAK  12/09/12 13:53:08     ACTIVE           sqlplus.exe

可以看到该online的回滚段是sqlplus.exe的一个会话，这个是我另一个连接该数据库的sqlplus窗口，将该窗口关掉再查看回滚段状态。SQL> alter system kill session '131,24783';

5、各回滚段状态： SQL> select segment_name,tablespace_name,status from dba_rollback_segs;

SEGMENT_NAME                   TABLESPACE_NAME                STATUS------------------------------ ------------------------------ ----------------SYSTEM                         SYSTEM                         ONLINE_SYSSMU19_1323384053$          UNDOTBS1                       OFFLINE_SYSSMU18_2053914518$          UNDOTBS1                       OFFLINE_SYSSMU17_1486782901$          UNDOTBS1                       OFFLINE_SYSSMU16_65961640$            UNDOTBS1                       OFFLINE_SYSSMU15_2731980009$          UNDOTBS1                       OFFLINE_SYSSMU14_1272261740$          UNDOTBS1                       OFFLINE_SYSSMU13_3931036527$          UNDOTBS1                       OFFLINE_SYSSMU12_277474270$           UNDOTBS1                       OFFLINE_SYSSMU11_1127233206$          UNDOTBS1                       OFFLINE_SYSSMU10_2010384090$          UNDOTBS1                       OFFLINE_SYSSMU9_3385418537$           UNDOTBS1                       OFFLINE_SYSSMU8_960788264$            UNDOTBS1                       OFFLINE_SYSSMU7_2218399740$           UNDOTBS1                       OFFLINE_SYSSMU6_4013851069$           UNDOTBS1                       OFFLINE_SYSSMU5_14816259$             UNDOTBS1                       OFFLINE_SYSSMU4_3531847310$           UNDOTBS1                       OFFLINE_SYSSMU3_3898657637$           UNDOTBS1                       OFFLINE_SYSSMU2_2881644447$           UNDOTBS1                       OFFLINE_SYSSMU1_1093178884$           UNDOTBS1                       OFFLINE_SYSSMU43_2526432190$          UNDOTBS2                       ONLINE_SYSSMU42_1073097992$          UNDOTBS2                       ONLINE_SYSSMU41_4185790622$          UNDOTBS2                       ONLINE_SYSSMU40_4075868025$          UNDOTBS2                       ONLINE_SYSSMU39_1225046965$          UNDOTBS2                       ONLINE_SYSSMU38_1416928319$          UNDOTBS2                       ONLINE_SYSSMU37_425218863$           UNDOTBS2                       ONLINE_SYSSMU36_2283506252$          UNDOTBS2                       ONLINE_SYSSMU35_3741949710$          UNDOTBS2                       ONLINE_SYSSMU34_3108701464$          UNDOTBS2                       ONLINE_SYSSMU33_1440052939$          UNDOTBS2                       ONLINE_SYSSMU31_867868996$           UNDOTBS2                       ONLINE_SYSSMU30_4206031811$          UNDOTBS2                       ONLINE_SYSSMU29_1581029439$          UNDOTBS2                       ONLINE_SYSSMU28_2713846431$          UNDOTBS2                       ONLINE_SYSSMU27_2818503999$          UNDOTBS2                       ONLINE_SYSSMU26_3492104676$          UNDOTBS2                       ONLINE_SYSSMU25_231788078$           UNDOTBS2                       ONLINE_SYSSMU24_494800911$           UNDOTBS2                       ONLINE_SYSSMU23_3011088732$          UNDOTBS2                       ONLINE_SYSSMU22_358374592$           UNDOTBS2                       ONLINE_SYSSMU21_3370208409$          UNDOTBS2                       ONLINE

已选择42行。

6、此时该回滚段已经变成了offline状态，将该回滚段drop掉即可SQL> drop tablespace undotbs1 including contents and datafiles;

7、至此，重建过程结束。