现在我们可以采用如下步骤回收UNDO空间:
1.确认文件
SQL> select file_name,bytes/1024/1024 from dba_data_files
2 where tablespace_name like 'UNDOTBS1';
FILE_NAME
--------------------------------------------------------------------------------
BYTES/1024/1024
---------------
+ORADG/danaly/datafile/undotbs1.265.600173875
27810
2.检查UNDO Segment状态
SQL> select usn,xacts,rssize/1024/1024/1024,hwmsize/1024/1024/1024,shrinks
2 from v$rollstat order by rssize;
USN XACTS RSSIZE/1024/1024/1024 HWMSIZE/1024/1024/1024 SHRINKS
---------- ---------- --------------------- ---------------------- ----------
0 0 .000358582 .000358582 0
2 0 .071517944 .071517944 0
3 0 .13722229 .13722229 0
9 0 .236984253 .236984253 0
10 0 .625144958 .625144958 0
5 1 1.22946167 1.22946167 0
8 0 1.27175903 1.27175903 0
4 1 1.27895355 1.27895355 0
7 0 1.56770325 1.56770325 0
1 0 2.02474976 2.02474976 0
6 0 2.9671936 2.9671936 0
11 rows selected.
3.创建新的UNDO表空间
SQL> create undo tablespace undotbs2;
Tablespace created.
4.切换UNDO表空间为新的UNDO表空间
SQL> alter system set undo_tablespace=undotbs2 scope=both;
System altered.
此处使用spfile需要注意，以前曾经记录过这样一个案例，Oracle诊断案例-Spfile案例一则。另外，如果使用的RAC环境，请注意，修改spfile时，要指定sid参数。
5.等待原UNDO表空间所有UNDO SEGMENT OFFLINE
SQL> select usn,xacts,status,rssize/1024/1024/1024,hwmsize/1024/1024/1024,shrinks
2 from v$rollstat order by rssize;
USN XACTS STATUS RSSIZE/1024/1024/1024 HWMSIZE/1024/1024/1024 SHRINKS
---------- ---------- --------------- --------------------- ---------------------- ----------
14 0 ONLINE .000114441 .000114441 0
19 0 ONLINE .000114441 .000114441 0
11 0 ONLINE .000114441 .000114441 0
12 0 ONLINE .000114441 .000114441 0
13 0 ONLINE .000114441 .000114441 0
20 0 ONLINE .000114441 .000114441 0
15 1 ONLINE .000114441 .000114441 0
16 0 ONLINE .000114441 .000114441 0
17 0 ONLINE .000114441 .000114441 0
18 0 ONLINE .000114441 .000114441 0
0 0 ONLINE .000358582 .000358582 0
USN XACTS STATUS RSSIZE/1024/1024/1024 HWMSIZE/1024/1024/1024 SHRINKS
---------- ---------- --------------- --------------------- ---------------------- ----------
6 0 PENDING OFFLINE 2.9671936 2.9671936 0
12 rows selected.
等候一段时间，再次查看:
11:32:11 SQL> /
USN XACTS STATUS RSSIZE/1024/1024/1024 HWMSIZE/1024/1024/1024 SHRINKS
---------- ---------- --------------- --------------------- ---------------------- ----------
15 1 ONLINE .000114441 .000114441 0
11 0 ONLINE .000114441 .000114441 0
12 0 ONLINE .000114441 .000114441 0
13 0 ONLINE .000114441 .000114441 0
14 0 ONLINE .000114441 .000114441 0
20 0 ONLINE .000114441 .000114441 0
16 0 ONLINE .000114441 .000114441 0
17 0 ONLINE .000114441 .000114441 0
18 0 ONLINE .000114441 .000114441 0
19 0 ONLINE .000114441 .000114441 0
0 0 ONLINE .000358582 .000358582 0
11 rows selected.
Elapsed: 00:00:00.00
6.删除原UNDO表空间
11:34:00 SQL> drop tablespace undotbs1 including contents;
Tablespace dropped.
Elapsed: 00:00:03.13
7.检查空间情况
由于我使用的ASM管理,可以使用10gR2提供的信工具asmcmd来察看空间占用情况.
[oracle@danaly ~]$ export ORACLE_SID=+ASM
[oracle@danaly ~]$ asmcmd
ASMCMD> du
Used_MB Mirror_used_MB
21625 21625
ASMCMD> exit
至此空间已经释放。
