[20190419]shared latch spin count 2.txt
--//上午测试shared latch XX模式的情况,链接:http://blog.itpub.net/267265/viewspace-2641902/
--//继续测试其它情况.
--//链接:http://andreynikolaev.wordpress.com/2011/01/14/spin-tales-part-2-shared-latches-in-oracle-9-2-11g/
S mode get X mode get
Held in S mode Compatible 2*_spin_count
Held in X mode 0 2*_spin_count
Blocking mode 0 2*_spin_count
1.环境:
SCOTT@book> @ ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
SYS@book> @ hide spin_count
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
----------------- ---------------------------------- ------------- ------------- ------------
_mutex_spin_count Mutex spin count TRUE 255 255
_spin_count Amount to spin waiting for a latch TRUE 2000 2000
$ cat shared_latch.txt
/* 参数如下: @ latch.txt latch_name willing why where mode sleep_num */
--//connect / as sysdba
col laddr new_value laddr
col vmode new_value vmode
select decode(lower('&&5'),'s',8,'x',16,'8',8,'16',16) vmode from dual ;
SELECT addr laddr FROM v$latch_parent WHERE NAME='&&1';
oradebug setmypid
oradebug call kslgetsl_w 0x&laddr &&2 &&3 &&4 &vmode
host sleep &&6
oradebug call kslfre 0x&laddr
--//exit
--//注:我前几天的测试脚本有connect / as sysdba,exit这两行,我为了调式方便,先注解这2行,避免反复退出进入会话.
2.测试1:
--//选择一个shared latch测试,我选择"test shared non-parent l0" latch测试:
SYS@book> select * from shared_latches where name='test shared non-parent l0';
VERSION LATCH# NAME S
---------- ------ ------------------------- -
11.2.0.4.0 6 test shared non-parent l0 Y
2.测试一些细节不再列出,参考链接:http://blog.itpub.net/267265/viewspace-2641902/
--//测试XS模式的情况:
--//session 1:
SYS@book> @ shared_latch.txt "test shared non-parent l0&