查询到表空间有个对象占用空间非常大，达200G

SQL> select * from (

2 select owner,segment_name,tablespace_name,segment_type,bytes/1024/1024 from dba_segments order by 5 desc

) where TABLESPACE_NAME='USERS' AND rownum<20; 3

OWNER SEGMENT_NAME

------------------------------ -----------------------------------

TABLESPACE_NAME SEGMENT_TYPE BYTES/1024/1024

------------------------------ ------------------ ---------------

UNIGUARD SYS_LOB0000052424C00006$$

USERS LOBSEGMENT 204859

UNIGUARD IMAGE_FILE

USERS TABLE 10826

UNIGUARD CAR_TRACK_10

USERS TABLE 4097

LOBSEGMENT的系统命名规则是

SYS_LOB(10 digit object_id)C(5 digit col#)$$   表段

SYS_IL(10 digit object_id)C(5 digit col#)$$        索引

SQL> select object_name,status from dba_objects where object_id='0000052424';

OBJECT_NAME

--------------------------------------------------------------------------------

STATUS

-------

IMAGE_FILE

VALID 原来是image_file使用了lob字段，为了释放出空间，我把此表导出，重建，再导入。结果空间释放。