[20190214]11g Query Result Cache RC Latches补充.txt

--//上午测试链接:http://blog.itpub.net/267265/viewspace-2632907/

--//发现自己的一个错误,另外写一篇帖子更正.

--//顺便复习result cache的相关内容:链接:https://blog.csdn.net/jolly10/article/details/81382644

查看SQL结果高速缓存字典信息

(G)V$RESULT_CACHE_STATISTICS : 列出各种高速缓存设置和内存使用量统计信息

(G)V$RESULT_CACHE_MEMORY : 列出所有内存块和相应的统计信息

(G)V$RESULT_CACHE_OBJECTS: 列出所有对象（高速缓存结果和依赖性）及其属性

(G)V$RESULT_CACHE_DEPENDENCY: 列出高速缓存结果之间的依赖性详细信息及依赖性

dbms_result_cache包可以监视和管理result cache

例如:

dbms_result_cache.flush：清除result cache。

dbms_result_cache.invalidate(owner,name)：使某对象的result cache无效。

dbms_result_cache.status：显示result cache的状态。

dbms_result_cache.memory_report：显示result cache的内存使用状况。

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

SCOTT@book> create table job_times ( sid   number, time_ela number);

Table created.

SCOTT@book> create table hc_t ( n number(*,0), v varchar2(200)) ;

Table created.

SCOTT@book> insert into hc_t select level, dbms_random.string('p', 200) from dual connect by level <= 10000;

10000 rows created.

SCOTT@book> create unique index i_hc_t on hc_t(n);

Index created.

SCOTT@book> commit;

Commit complete.

--//分析表略.

create or replace procedure do_rc(

 p_iterations in number,p_max in number

) is

 l_rowid  rowid;

 l_n number;

begin

 insert into job_times

  values (sys_context('userenv', 'sid'), dbms_utility.get_time)

  returning rowid into l_rowid;

 for i in 1 .. p_iterations

 loop

  l_n:=trunc(dbms_random.value(1, p_max));

  for cur in (select /*+ result_cache */ * from hc_t where n=l_n)

  loop

   null;

  end loop;

 end loop;

 update job_times set

   time_ela=dbms_utility.get_time-time_ela

  where rowid=l_rowid;

end;

/

--//注:我加入参数p_max,限制取值范围.

--//为了重复测试建立脚本.

$ cat aa.sql

delete from job_times;

Commit ;

declare

 l_job number;

begin

 for i in 1 .. 4

 loop

  dbms_job.submit(

   job => l_job,

   what => 'do_rc(100000,&&1);'

    );

 end loop;

end;

/

commit ;

2.开始测试:

SCOTT@book> show parameter result

NAME                                 TYPE         VALUE

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

client_result_cache_lag              big integer  3000

client_result_cache_size             big integer  0

result_cache_max_result              integer      5

result_cache_max_size                big integer  1792K

result_cache_mode                    string       MANUAL

result_cache_remote_expiration       integer      0

SCOTT@book> exec dbms_result_cache.flush()

PL/SQL procedure successfully completed.

SCOTT@book> set serverout on

SCOTT@book> exec dbms_result_cache.memory_report

R e s u l t   C a c h e   M e m o r y   R e p o r t

[Parameters]

Block Size          = 0 bytes

Maximum Cache Size  = 0 bytes (0 blocks)

Maximum Result Size = 0 bytes (0 blocks)

[Memory]

Total Memory = 40568 bytes [0.022% of the Shared Pool]

... Fixed Memory = 40568 bytes [0.022% of the Shared Pool]

... Dynamic Memory = 0 bytes [0.000% of the Shared Pool]

PL/SQL procedure successfully completed.

--//我前面测试忽略的result cache的大小.

SCOTT@book> @ aa.sql 10000

4 rows deleted.

Commit complete.

PL/SQL procedure successfully completed.

Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;

  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)

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

         4        4001.5         16006

--//以上我上午测试的结果.大约每个job需要40秒上下.

SCOTT@book> exec dbms_result_cache.memory_report

R e s u l t   C a c h e   M e m o r y   R e p o r t

[Parameters]

Block Size          = 1K bytes

Maximum Cache Size  = 1792K bytes (1792 blocks)

Maximum Result Size = 89K bytes (89 blocks)

[Memory]

Total Memory = 2003960 bytes [1.111% of the Shared Pool]

... Fixed Memory = 40568 bytes [0.022% of the Shared Pool]

... Dynamic Memory = 1963392 bytes [1.089% of the Shared Pool]

....... Overhead = 128384 bytes

....... Cache Memory = 1792K bytes (1792 blocks)

........... Unused Memory = 0 blocks

........... Used Memory = 1792 blocks

............... Dependencies = 1 blocks (1 count)

............... Results = 1791 blocks

................... SQL     = 1791 blocks (1791 count)

PL/SQL procedure successfully completed.

--//实际上我的环境仅仅能容纳1791个结果.也就是我的配置太小,共享池不够大.result_cache_max_result=5,仅仅使用共享池的5%.

SCOTT@book> @ aa.sql 1791

4 rows deleted.

Commit complete.

PL/SQL procedure successfully completed.

Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;

  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)

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

         4         440.5          1762

--//你可以发现这个就与没有做result cache的结果相近了.

--//我重启数据库.通过result cache :RC latch记数也可以验证这个问题.

SCOTT@book> column name format a30

SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';

NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME

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

Result Cache: RC Latch                  0          0          0          0

Result Cache: SO Latch                  0          0          0          0

Result Cache: MB Latch                  0          0          0          0

SCOTT@book> @ aa.sql 1791

4 rows deleted.

Commit complete.

PL/SQL procedure successfully completed.

Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;

  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)

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

         4           432          1728

SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';

NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME

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

Result Cache: RC Latch             405177       3865         10        132

Result Cache: SO Latch                  8          0          0          0

Result Cache: MB Latch                  0          0          0          0

SCOTT@book> @ aa.sql 10000

4 rows deleted.

Commit complete.

PL/SQL procedure successfully completed.

Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;

  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)

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

         4       3978.25         15913

SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';

NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME

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

Result Cache: RC Latch            1787843     534395     683654   67269002

Result Cache: SO Latch                 16          0          0          0

Result Cache: MB Latch                  0          0          0          0