Shrink Undo表空间,释放过度占用的空间

环境:
OS:Red Hat Enterprise Linux AS release 4 (Nahant)
DB:Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - ProdUCtion
一台Oracle10gR2数据库报出如下错误:

ORA-1653: unable to extend table SYSMAN.MGMT_SYSTEM_ERROR_LOG by 8 in tablespace SYSAUX ORA-1653: unable to extend table SYSMAN.MGMT_SYSTEM_ERROR_LOG by 8 in tablespace SYSAUX ORA-1653: unable to extend table SYSMAN.MGMT_SYSTEM_ERROR_LOG by 8 in tablespace SYSAUX ORA-1653: unable to extend table SYSMAN.MGMT_SYSTEM_ERROR_LOG by 8 in tablespace SYSAUX ORA-1653: unable to extend table SYSMAN.MGMT_SYSTEM_ERROR_LOG by 8 in tablespace SYSAUX
登陆检查，发现是SYSAUX表空间空间用尽,不能扩展,尝试手工扩展SYSAUX表空间:
alter database datafile '+ORADG/danaly/datafile/sysaux.266.600173881' resize 800m Tue Nov 29 23:31:38 2005 ORA-1237 signalled during: alter database datafile
'+ORADG/danaly/datafile/sysaux.266.600173881' resize 800m...
出现ORA-1237错误，提示空间不足。这时候我才熟悉到是磁盘空间可能被用完了.

是谁"偷偷的"用了那么多空间呢(本来有几十个G的Free磁盘空间的)?
检查数据库表空间占用空间情况:
SQL> select tablespace_name,sum(bytes)/1024/1024/1024 GB 2 from dba_data_files group by tablespace_name 3 union all 4 select tablespace_name,sum(bytes)/1024/1024/1024 GB 5 from dba_temp_files group by tablespace_name order by GB; TABLESPACE_NAME GB ------------------------------ ---------- USERS .004882813 UNDOTBS2 .09765625 SYSTEM .478515625 SYSAUX .634765625 WAPCM_TS_VISIT_DETAIL .9765625 HY_DS_DEFAULT 1 MINT_TS_DEFAULT 1 MMS_TS_DATA2 1.375 MMS_IDX_SJH 2 MMS_TS_DEFAULT 2 IVRCN_TS_DATA 2 TABLESPACE_NAME GB ------------------------------ ---------- MMS_TS_DATA1 2 CM_TS_DEFAULT 5 TEMP 20.5498047 UNDOTBS1 27.1582031 15 rows selected.
不幸的发现，UNDO表空间已经扩展至27G，而TEMP表空间也扩展至20G，这2个表空间加起来占用了47G的磁盘空间,导致了空间不足。
显然曾经有大事务占用了大量的UNDO表空间和Temp表空间，Oracle的AUM(Auto Undo Management)从出生以来就经常出现只扩展,不收缩(shrink)的情况(通常我们可以设置足够的UNDO表空间大小,然后取消其自动扩展属性).
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$rollstat order by rssize; USN XACTS RSSIZE/1024/1024/1024 HWMSIZE/1024/1024/1024 SHRINKS ---------- ---------- --------------------- ---------------------- ---------- 0 0 .000358582 .000358582 0 2 0 .071517944 .071517944 0 3 0 .13722229 .13722229 0 9 0 .236984253 .236984253 0 10 0 .625144958 .625144958 0 5 1 1.22946167 1.22946167 0 8 0 1.27175903 1.27175903 0 4 1 1.27895355 1.27895355 0 7 0 1.56770325 1.56770325 0 1 0 2.02474976 2.02474976 0 6 0 2.9671936 2.9671936 0 11 rows selected.
3.创建新的UNDO表空间
SQL> create undo tablespace undotbs2; Tablespace created.
4.切换UNDO表空间为新的UNDO表空间
SQL> alter system set undo_tablespace=undotbs2 scope=both; System altered.
此处使用spfile需要注重，以前曾经记录过这样一个案例:Oracle诊断案例-Spfile案例一则
5.等待原UNDO表空间所有UNDO SEGMENT OFFLINE SQL> select usn,xacts,status,rssize/1024/1024/1024,hwmsize/1024/1024/1024,shrinks 2 from v$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.
再看:
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治理,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
空间已经释放。