ORACLE UNDO表空间回收处理

目前有一个10g的数据库在检查时发现undo表空间异常庞大，undo表空间占了将近45G

1、首先查询当前undo表空间的使用情况，有文件使用已经达到32G

SQL> select file_name,bytes/1024/1024 MB,autoextensible from dba_data_files where tablespace_name like 'UNDOTBS1';

FILE_NAME                          MB    AUT
---------------------------------------- ----------   ---
D:\ORADB\ORADATA\ORCL\UNDOTBS01.DBF     32767.9844 YES
D:\ORADB\ORADATA\ORCL\UNDOTBS02.DBF         8192 YES
D:\ORADB\ORADATA\ORCL\UNDOTBS03.DBF         4096 YES

2、查看当前undo的参数

SQL> show parameter undo;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     900
undo_tablespace                      string      UNDOTBS1

3、采取重建undo表空间的方法来，取消自动扩展

create undo tablespace undotbs2 datafile 'D:\ORADB\ORADATA\ORCL\UNDOTBS201.DBF' size 4G autoextend off;
alter tablespace undotbs2 add datafile 'D:\ORADB\ORADATA\ORCL\UNDOTBS202.DBF' size 4G autoextend off ;
alter tablespace undotbs2 add datafile 'D:\ORADB\ORADATA\ORCL\UNDOTBS203.DBF' size 4G autoextend off;
4、切换undo表空间

SQL>alter system set undo_tablespace=undotbs2 scope=both;

SQL> show parameter undo

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     900
undo_tablespace                      string      UNDOTBS2

5、查看当前的undo1 的回滚段状态

SQL> select segment_name,tablespace_name,status from dba_rollback_segs t where tablespace_name='UNDOTBS1' and status='OLINE';

SEGMENT_NAME                   TABLESPACE_NAME                STATUS
------------------------------ ------------------------------ ----------------
_SYSSMU9$                      UNDOTBS1                       ONLINE
_SYSSMU10$                     UNDOTBS1                       ONLINE

6、由于上面的两个回滚段一直处于online状态，无法直接删除undotbs1表空间和数据文件回收空间，首先试着使用命令下线回滚段

SQL>  ALTER ROLLBACK SEGMENT "_SYSSMU9$" OFFLINE;

Rollback segment altered.

7、查询回滚段状态，一直处于pengding offline状态

SQL> SELECT s.username, u.name ,r.status FROM v$transaction t, v$rollstat r, v$rollname u, v$session s WHERE s.taddr = t.addr AND t.xidusn = r.usn AND r.usn
= u.usn ORDER BY s.username;

USERNAME                    NAME                           STATUS
--------------------------- ------------------------------ ---------------
u01                         _SYSSMU10$                     PENDING OFFLINE
u02                         _SYSSMU505$                    ONLINE
u02                         _SYSSMU501$                    ONLINE
u02                         _SYSSMU9$                      PENDING OFFLINE
u02                         _SYSSMU497$                    ONLINE
u02                         _SYSSMU506$                    ONLINE

6 rows selected.

8、查找到相关的事务ID

SQL> SELECT s.sid,serial#, u.name ,r.status
2  FROM v$transaction t, v$rollstat r, v$rollname u, v$session s
3  WHERE s.taddr = t.addr AND t.xidusn = r.usn AND r.usn = u.usn and r.status='PENDING OFFLINE' ;

SID    SERIAL# NAME                           STATUS
---------- ---------- ------------------------------ ---------------
3150      18393 _SYSSMU9$                      PENDING OFFLINE
3175       9695 _SYSSMU10$                     PENDING OFFLINE

9、根据上面的SID号查询该会话正在执行的操作

select sql_text from v$session a,v$sqltext_with_newlines b
where DECODE(a.sql_hash_value, 0, prev_hash_value, sql_hash_value)=b.hash_value
and a.sid=&sid order by piece;

10、结束该会话

alter system kill session '3150,18393';
alter system kill session '3175,9695';
ALTER ROLLBACK SEGMENT "_SYSSMU9$" OFFLINE;
ALTER ROLLBACK SEGMENT "_SYSSMU10$" OFFLINE;

11、验证当前undotbs1 是否全部offline

select * from dba_rollback_segs t where tablespace_name='UNDOTBS1' and status='ONLINE';

12、删除掉undotbs1

SQL> drop tablespace undotbs1 including contents and datafiles;

Tablespace dropped.

SQL> SELECT   tablespace_name, status, SUM (bytes) / 1024 / 1024 "Bytes(M)"
2      FROM   dba_undo_extents
3  GROUP BY   tablespace_name, status;

TABLESPACE_NAME                STATUS      Bytes(M)
------------------------------ --------- ----------
UNDOTBS2                       UNEXPIRED    29.8125
UNDOTBS2                       EXPIRED      50.1875
UNDOTBS2                       ACTIVE             3