[20200212]使用DBMS_SHARED_POOL.MARKHOT与sql的计算2.txt

--//昨天的测试：http://blog.itpub.net/267265/viewspace-2675128/ =>[20200211]使用DBMS_SHARED_POOL.MARKHOT与sql_id的计算.txt
--//补充测试设置隐含参数_kgl_hot_object_copies的情况：

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> alter system set "_kgl_hot_object_copies"=101 scope=spfile ;
System altered.
--//必须重启才生效，重启数据库略。

SYS@book> @ hide _kgl_hot_object_copies
NAME                   DESCRIPTION                         DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ISSES ISSYS_MOD
---------------------- ----------------------------------- ------------- ------------- ------------ ----- ---------
_kgl_hot_object_copies Number of copies for the hot object FALSE         101           101          FALSE FALSE

SCOTT@book> select * from dept where deptno=10;
    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
--//sql_id='4xamnunv51w9j',可以执行多次,避免sql语句退出共享池.

SELECT name
      ,hash_value
      ,full_hash_value
      ,namespace
      ,child_latch
      ,property hot_flag
      ,executions
      ,invalidations
  FROM v$db_object_cache
 WHERE name = 'select * from dept where deptno=10';

NAME                                     HASH_VALUE FULL_HASH_VALUE                  NAMESPACE  CHILD_LATCH HOT_FLAG   EXECUTIONS INVALIDATIONS
---------------------------------------- ---------- -------------------------------- ---------- ----------- ---------- ---------- -------------
select * from dept where deptno=10        911274289 1431c45dbddbb9e74eaa74d53650f131 SQL AREA             0                     6             0
select * from dept where deptno=10        911274289 1431c45dbddbb9e74eaa74d53650f131 SQL AREA         61745                     6             0
--//确定FULL_HASH_VALUE='1431c45dbddbb9e74eaa74d53650f131'.

$ echo -e -n  'select * from dept where deptno=10\0' | md5sum | sed 's/  -//' | xxd -r -p | od -t x4 | sed  -n  -e 's/^0000000 //' -e 's/ //gp'
1431c45dbddbb9e74eaa74d53650f131
--//对比完全能对上。

2.测试：
--//首先使用DBMS_SHARED_POOL.MARKHOT标记。
SYS@book> exec dbms_shared_pool.markhot( hash=>'1431c45dbddbb9e74eaa74d53650f131', namespace=>0, global=>true);
PL/SQL procedure successfully completed.

--//以scott登录
--//session 1:
SCOTT@book> @ spid
       SID    SERIAL# PROCESS                  SERVER    SPID       PID  P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
       295          7 63251                    DEDICATED 63252       21          4 alter system kill session '295,7' immediate;

SCOTT@book> select * from dept where deptno=10;
    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK

--//session 2:

SYS@book> select sql_id,sql_text,executions,length(sql_text),ora_hash(sql_text) from v$sqlarea where sql_text = 'select * from dept where deptno=10' ;
SQL_ID        SQL_TEXT                                                     EXECUTIONS LENGTH(SQL_TEXT) ORA_HASH(SQL_TEXT)
------------- ------------------------------------------------------------ ---------- ---------------- ------------------
atpswbzn2drda select * from dept where deptno=10                                    1               34          156172166
4xamnunv51w9j select * from dept where deptno=10                                    6               34          156172166
--//sql_id=atpswbzn2drda select

SELECT name
      ,hash_value
      ,full_hash_value
      ,namespace
      ,child_latch
      ,property hot_flag
      ,executions
      ,invalidations
  FROM v$db_object_cache
 WHERE name = 'select * from dept where deptno=10';

NAME                                     HASH_VALUE FULL_HASH_VALUE                  NAMESPACE  CHILD_LATCH HOT_FLAG   EXECUTIONS INVALIDATIONS
---------------------------------------- ---------- -------------------------------- ---------- ----------- ---------- ---------- -------------
select * from dept where deptno=10       3894861226 6b47602c1c49a6baacd71c5fe826ddaa SQL AREA             0 HOTCOPY94           1             0
select * from dept where deptno=10       3894861226 6b47602c1c49a6baacd71c5fe826ddaa SQL AREA         56746 HOTCOPY94           1             0
select * from dept where deptno=10        911274289 1431c45dbddbb9e74eaa74d53650f131 SQL AREA             0 HOT                 6             0
select * from dept where deptno=10        911274289 1431c45dbddbb9e74eaa74d53650f131 SQL AREA         61745 HOT                 6             0

--//HOT_FLAG='HOTCOPY94'

$ ./sql_id.sh 'select * from dept where deptno=10\0.94'
sql_text = select * from dept where deptno=10\0.94
full_hash_value(16) = 6b47602c1c49a6baacd71c5fe826ddaa
hash_value(10) = 3894861226
sql_id(32) = atpswbzn2drda
sql_id(32) = atpswbzn2drda
sql_id(32) = atpswbzn2drda

--//sql_idm以及full_hash_value完全对上。

3.验证看看是否通过sid取模确定HOT_FLAG。
--//session 1:
SCOTT@book> @ spid

       SID    SERIAL# PROCESS                  SERVER    SPID       PID  P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
       295          7 63251                    DEDICATED 63252       21          4 alter system kill session '295,7' immediate;

SCOTT@book> select mod(295 ,101)+1 from dual ;
MOD(295,101)+1
--------------
            94
--//OK，完全正确。

4.总结：
--//sql语句使用使用DBMS_SHARED_POOL.MARKHOT标记热的sql_id时，full_hash_value和sql_id的计算,就是在原来sql语句的基础
--//上加上 . mod(sid,cpu_count/2)+1数字的字符串，注前面的测试有误，应该是cpu_count/2而不是cpu_count，特此更正。
--//原链接：http://blog.itpub.net/267265/viewspace-2675128/ => [20200211]使用DBMS_SHARED_POOL.MARKHOT与sql_id的计算.txt
--//如果设置隐含参数_kgl_hot_object_copies，变为加上 . mod(sid,_kgl_hot_object_copies)+1数字的字符串。