Oracle如何回收回滚段空间


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需要注意,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

  空间已经释放



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