V$SESSION中有如下4個列，用來記錄當發生enq:TX-row lock contention的時候，
導致掛起的行。
ROW_WAIT_OBJ# NUMBER --包含該記錄的OBJECT_ID
ROW_WAIT_FILE# NUMBER --該記錄所在的相對文件號
ROW_WAIT_BLOCK# NUMBER --該記錄所在的BLOCK號
ROW_WAIT_ROW# NUMBER --該記錄所在塊中的行號
大部分人採用如下的SQL來查詢引起堵塞的行：
select c.OBJECT_NAME,a.ROW_WAIT_OBJ#,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#,
dbms_rowid.rowid_create(1,c.OBJECT_ID,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#) rid
from v$session a , v$enqueue_lock b, dba_objects c
where a.sid=b.SID and b.type='TX' and a.ROW_WAIT_OBJ#=object_id(+)
而且一般情況下是沒問題的。
如下：
SESSION 1：
SQL> select rowid from test where rownum=1;
ROWID
------------------
AAp/YEAAFAACmXkAAA
SQL> delete from test where rownum=1;
1 row deleted.
SQL>
SESSION 2：
SQL> update test set object_name=object_name where rownum=1;
SESSION 2將會被HANG住。
通過另外的SESSION執行如下的查詢可以看到引起堵塞的記錄是
TEST表的ROWID=‘AAp/YEAAFAACmXkAAA’的記錄。
SQL> select c.OBJECT_NAME,a.ROW_WAIT_OBJ#,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#,
2 dbms_rowid.rowid_create(1,c.OBJECT_ID,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#) rid
3 from v$session a , v$enqueue_lock b, dba_objects c
4 where a.sid=b.SID and b.type='TX' and a.ROW_WAIT_OBJ#=object_id(+);
OBJECT_NAM ROW_WAIT_OBJ# ROW_WAIT_FILE# ROW_WAIT_BLOCK# ROW_WAIT_ROW# RID
---------- ------------- -------------- --------------- ------------- ------------------------------------
TEST 11007492 5 681444 0 AAp/YEAAFAACmXkAAA
SQL> select rowid,object_id from scott.test where rowid='AAp/YEAAFAACmXkAAA';
ROWID OBJECT_ID
------------------ ----------
AAp/YEAAFAACmXkAAA 258
SQL> select rowid,object_id from scott.test where rowid='AAp/YEAAFAACmXkAAA' for update skip locked;
no rows selected
但是這是在TEST表的OBJECT_ID和DATA_OBJECT_ID一致的情況下才行。
SQL> select object_id,data_object_id from user_objects where object_name='TEST';
OBJECT_ID DATA_OBJECT_ID
---------- --------------
11007492 11007492
一旦OBJECT_ID和DATA_OBJECT_ID不一樣，那麼查詢結果將是錯誤的。
因爲V$SESSION.ROW_WAIT_OBJ#記錄的是對象的OBJECT_ID
而DBMS_ROWID.CREATE_ROWID需要的是對象的DATA_OBJECT_ID
如下:
SESSION 1:
SQL> alter table test move;
Table altered.
SQL> select object_id,data_object_id from user_objects where object_name='TEST';
OBJECT_ID DATA_OBJECT_ID
---------- --------------
11007492 11007579
SQL> select rowid from test where rownum=1;
ROWID
------------------
AAp/ZbAAFAACmjsAAA
SQL> delete from test where rownum=1;
1 row deleted.
SQL>
SESSION 2:
SQL> update test set object_name=object_name where rownum=1;
將會HANG住。
SESSION 3:
SQL> select c.OBJECT_NAME,a.ROW_WAIT_OBJ#,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#,
2 dbms_rowid.rowid_create(1,c.OBJECT_ID,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#) rid
3 from v$session a , v$enqueue_lock b, dba_objects c
4 where a.sid=b.SID and b.type='TX' and a.ROW_WAIT_OBJ#=object_id(+)
5 /
OBJECT_NAM ROW_WAIT_OBJ# ROW_WAIT_FILE# ROW_WAIT_BLOCK# ROW_WAIT_ROW# RID
---------- ------------- -------------- --------------- ------------- ------------------------------------
TEST 11007492 5 682220 0 AAp/YEAAFAACmjsAAA
SQL> SELECT rowid from scott.test where rowid='AAp/YEAAFAACmjsAAA';
SELECT rowid from scott.test where rowid='AAp/YEAAFAACmjsAAA'
*
ERROR at line 1:
ORA-01410: invalid ROWID
ROWID_CREATE中的C.ROW_WAIT_OBJ#需要改爲DATA_OBJECT_ID才行。
SQL> select c.OBJECT_NAME,a.ROW_WAIT_OBJ#,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#,
2 dbms_rowid.rowid_create(1,c.DATA_OBJECT_ID,a.ROW_WAIT_FILE#,a.ROW_WAIT_BLOCK#,a.ROW_WAIT_ROW#) rid
3 from v$session a , v$enqueue_lock b, dba_objects c
4 where a.sid=b.SID and b.type='TX' and a.ROW_WAIT_OBJ#=object_id(+);
OBJECT_NAM ROW_WAIT_OBJ# ROW_WAIT_FILE# ROW_WAIT_BLOCK# ROW_WAIT_ROW# RID
---------- ------------- -------------- --------------- ------------- ------------------------------------
TEST 11007492 5 682220 0 AAp/ZbAAFAACmjsAAA
SQL> SELECT rowid from scott.test where rowid='AAp/ZbAAFAACmjsAAA';
ROWID
------------------
AAp/ZbAAFAACmjsAAA