object_id和data_object_id区别与联系

http://www.xifenfei.com/1553.html

object_id和data_object_id区别与联系

发表于 2011 年 09 月 12 日 由 惜分飞

链接：http://www.xifenfei.com/1553.html

标题：object_id和data_object_id区别与联系

作者：惜分飞©版权所有[文章允许转载,但必须以链接方式注明源地址,否则追究法律责任.]

其实object_id和data_object_id同样是表示数据库对象的一个唯一标志，但是object_id表示的是逻辑 id，data_object_id表示的是物理id。如果一些object没有物理属性的话那它就不存在data_object_id，例如 procedure,function,package,data type,db link,mv定义,view定义,临时表,分区表定义等等这些object都是没有对应着某个segment，因此它们的data_object_id 都为空。

当表刚创建的时候它的object_id和data_object_id都是相等的，但是如果表经过move或truncate等，涉及到segment发生改变后data_object_id将会有变化。

DATA_OBJECT_ID was introduced in 8.0 to track versions of the same segment (certain operations change the version). It is used to discover stale ROWIDs and stale undo records.

SQL> create table xff as select * from dba_objects where rownum<100;

Table created

SQL> select object_id,data_object_id from user_objects where object_name='XFF';

 OBJECT_ID DATA_OBJECT_ID
---------- --------------
    211325         211325

SQL> alter table xff move;

Table altered

SQL> select object_id,data_object_id from user_objects where object_name='XFF';

 OBJECT_ID DATA_OBJECT_ID
---------- --------------
    211325         211326

SQL> truncate table xff;

Table truncated

SQL> create index ind_xff on xff(object_id);

Index created

SQL>  select object_id,data_object_id from user_objects where object_name='IND_XFF';

 OBJECT_ID DATA_OBJECT_ID
---------- --------------
    211328         211328

SQL> ALTER INDEX IND_XFF REBUILD;

Index altered

SQL>  select object_id,data_object_id from user_objects where object_name='IND_XFF';

 OBJECT_ID DATA_OBJECT_ID
---------- --------------
    211328         211329

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/16993226/viewspace-768949/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/16993226/viewspace-768949/