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SESSION 1：

SQL> select * from v$mystat where rownum<2;



       SID STATISTIC#	   VALUE

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

	 1	    0	       0



SQL> select * from a1;



	ID FLAG1      FLAG2

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

	 1 a	      a1

	 1 b	      b1



SQL> update a1 set id=2 where flag1='a';



1 row updated.





SESSION 2：

SQL>  update a1 set id=2 where flag1='a';





SQL> select * from v$lock;



ADDR	 KADDR		 SID TY        ID1	  ID2	   LMODE    REQUEST	 CTIME	    BLOCK

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

35000FE8 35001014	  12 XR 	 4	    0	       1	  0	   208		0

3500105C 35001088	  12 RD 	 1	    0	       1	  0	   208		0

350010D0 350010FC	  12 CF 	 0	    0	       2	  0	   208		0

350011B8 350011E4	  12 RS 	25	    1	       2	  0	   204		0

3500122C 35001258	   1 AE        100	    0	       4	  0	   123		0

350012A0 350012CC	  11 RT 	 1	    0	       6	  0	   204		0

35001314 35001340	  10 PW 	 1	    0	       3	  0	   200		0

35001388 350013B4	  13 TS 	 3	    1	       3	  0	   201		0

350013FC 35001428	  15 AE        100	    0	       4	  0	   195		0

35001470 3500149C	  10 MR 	 1	    0	       4	  0	   202		0

350014E4 35001510	  10 MR 	 2	    0	       4	  0	   202		0



ADDR	 KADDR		 SID TY        ID1	  ID2	   LMODE    REQUEST	 CTIME	    BLOCK

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

35001558 35001584	  10 MR 	 3	    0	       4	  0	   202		0

350015CC 350015F8	  10 MR 	 4	    0	       4	  0	   202		0

35001640 3500166C	  10 MR 	 5	    0	       4	  0	   202		0

350016B4 350016E0	  10 MR        201	    0	       4	  0	   202		0

35001728 35001754	  25 AE        100	    0	       4	  0	   180		0

3500179C 350017C8	  26 AE        100	    0	       4	  0	    94		0

35001810 3500183C	  17 AE        100	    0	       4	  0	   177		0

35001884 350018B0	  26 TX     393229	 9322	       0	  6	    92		0

350018F8 35001924	  31 AE        100	    0	       4	  0	     9		0

00FF8BF4 00FF8C24	  26 TM      75517	    0	       3	  0	    92		0

00FF8BF4 00FF8C24	   1 TM      75517	    0	       3	  0	   103		0



ADDR	 KADDR		 SID TY        ID1	  ID2	   LMODE    REQUEST	 CTIME	    BLOCK

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

33140924 33140964	   1 TX     393229	 9322	       6	  0	   103		1



23 rows selected.



SQL> select * from v$lock where sid in (1,26);



ADDR	 KADDR		 SID TY        ID1	  ID2	   LMODE    REQUEST	 CTIME	    BLOCK

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

3500122C 35001258	   1 AE        100	    0	       4	  0	   332		0

3500179C 350017C8	  26 AE        100	    0	       4	  0	   303		0

35001884 350018B0	  26 TX     393229	 9322	       0	  6	   301		0

01015210 01015240	  26 TM      75517	    0	       3	  0	   301		0

01015210 01015240	   1 TM      75517	    0	       3	  0	   312		0

33140924 33140964	   1 TX     393229	 9322	       6	  0	   312		1



6 rows selected.



SQL> create table a as select * from v$lock where sid in (1,26);



Table created.



SQL> create table b as select * from v$lock where sid in (1,26);



Table created.





SQL> select hold.sid, block.sid from a hold ,b block

where hold.id1=block.id1

and block.request<>0

and hold.sid<>block.sid  2    3    4  

  5  ;



       SID	  SID

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

	 1	   26