模拟cursor pin S wait on X

<pre name="code" class="sql">模拟cursor pin S wait on X

create table test tablespace users as select *from dba_objects;  

BEGIN
  DBMS_STATS.GATHER_TABLE_STATS(ownname          => 'TEST',
                                tabname          => 'TEST',
                                estimate_percent => 30,
                                method_opt       => 'for all columns size repeat',
                                no_invalidate    => FALSE,
                                degree           => 8,
                                cascade          => TRUE);
END;
/


测试开始:
这是10.2版本提出的mutex(互斥)机制用来解决library cache bin latch争夺问题引入的新事件,是否使用这种机制受到隐含参数_kks_use_mutex_pin的限制,从10.2.0.2开始该参数default为true,使用

这种机制oracle是为了解决library cache bin latch的串行使用问题,但是mutex貌似还不是很稳定,在很多系统中会出现cursor: pin S wait on X等待事件,这个事件和mutex的使用有关:
SQL> SELECT nam.ksppinm NAME, val.ksppstvl VALUE
  2  FROM x$ksppi nam, x$ksppsv val
  3  WHERE nam.indx = val.indx AND nam.ksppinm LIKE '%mutex%'
  4  ORDER BY 1;
NAME                                               VALUE
-------------------------------------------------- ----------------------------------------
_kks_use_mutex_pin                                 TRUE

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Prod
PL/SQL Release 10.2.0.4.0 - Production
CORE	10.2.0.4.0	Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

测试数据库版本:
SQL> SELECT nam.ksppinm NAME, val.ksppstvl VALUE
  FROM x$ksppi nam, x$ksppsv val
 WHERE nam.indx = val.indx
   AND nam.ksppinm LIKE '%mutex%'
 ORDER BY 1;  2    3    4    5  

NAME							     VALUE
------------------------------------------------------------ ----------
_kks_use_mutex_pin					     TRUE




select SESSION_ID,
ash.sample_time,
       NAME,
       P1,
       P2,
       P3,
       WAIT_TIME,
       CURRENT_OBJ#,
       CURRENT_FILE#,
       CURRENT_BLOCK#
  from v$active_session_history ash, v$event_name enm
 where ash.event# = enm.event#

        SESSION_ID   SANMPLE_TIME                 NAME                    P1            P2
1	1629	08-7月 -14 01.24.43.480 上午	cursor: pin S	          870994415	1	327689	0	-1	0	0
2	1629	08-7月 -14 01.24.42.480 上午	cursor: pin S	          870994415	1	327689	0	-1	0	0
3	1626	08-7月 -14 01.24.41.480 上午	cursor: pin S wait on X	  914340628	106758144	327686	0	-1	0	0
4	1627	08-7月 -14 01.24.40.480 上午	cursor: pin S	          1774050780	1	589825	0	-1	0	0
5	1626	08-7月 -14 01.24.39.470 上午	cursor: pin S wait on X	  202989082	106758144	327687	0	-1	0	0
6	1624	08-7月 -14 01.24.38.470 上午	cursor: pin S wait on X	  172408315	106758144	327685	0	-1	0	0
7	1624	08-7月 -14 01.24.37.470 上午	cursor: pin S	          4107572888	106627073	327687	0	-1	0	0
8	1634	08-7月 -14 01.24.37.470 上午	latch: library cache	  589581072	215	0	0	-1	0	0
9	1624	08-7月 -14 01.24.36.470 上午	cursor: pin S	          4107572888	106627073	327687	0	-1	0	0
10	1627	08-7月 -14 01.24.35.470 上午	latch: library cache	  589581072	215	0	0	-1	0	0
11	1634	08-7月 -14 01.24.35.470 上午	cursor: pin S wait on X	  4718305	106627072	327688	0	-1	0	0


select SESSION_ID,
ash.sample_time,
       NAME,
       P1,
       P2,
       P3,
       WAIT_TIME,
       CURRENT_OBJ#,
       CURRENT_FILE#,
       CURRENT_BLOCK#
  from v$active_session_history ash, v$event_name enm
 where ash.event# = enm.event#
1	1631	08-7月 -14 01.14.57.196 上午	cursor: pin S wait on X	3719301976	0	327681	0	-1	0	0


select b.*, sq.sql_text
  from v$session se,
       v$sql sq,
       (select a.*, s.sql_text
          from v$sql s,
               (select sid,
                       event,
                       wait_class,
                       p1,
                       p2raw,
                       to_number(substr(p2raw, 1, 4), 'xxxx') sid_hold_mutex_x
                  from v$session_wait
                 where event like 'cursor%') a
         where s.HASH_VALUE = a.p1) b
 where se.sid = b.sid
   and se.sql_hash_value = sq.hash_value;

        SID      EVENT                                                                 sid_hold_mutex_x
1	1637	cursor: pin S wait on X	Concurrency	4286791313	065F0000	1631	select object_id from test t where object_id=89	declare   v_string varchar2(100) 

:= 'alter system flush shared_pool';   msql     varchar2(200); begin   loop     for i in 1 .. 100 loop       msql := 'select object_id from test t where object_id=' || i;       

execute immediate msql;     end loop;   end loop; end;

                                                                    sid_hold_mutex_x 
1	1627	cursor: pin S	Other	868910173	065D0001	1629	select object_id from test t where object_id=3	select object_id from test t where object_id=3


                                                                                    sid_hold_mutex_x
2	1631	cursor: pin S wait on X	Concurrency	4107572888	065B0000	1627	select object_id from test t where object_id=100	select object_id from 

test t where object_id=60