oracle 11g 之 result cache

今天是2013-10-12，打算最近时间研究一下shared pool的相关原理以及awr报告分析。今天学习一下在oracle 11g shared pool中新增的一个cache 那就是result cache。

从上图可以看出在oracle 11g 的shared pool中存有对sql进行存储、存储sql执行计划、sql解析树等信息的library cache可以通过查看v$librarycahe视图了解其分配情况，以及row CACHE（data dictionary cache）可以查看v$rowcache视图了解其分配情况，对于这两部分内容咱不讨论，但是可以看一下如下这个图，大体明白这两个component的作用原理。

现在开始研究一下result cache，对于oracle 11g 分为client result cache以及server result cache，前者在client进行内存的分配，后者对于数据库server进行内存分配，现在看一下server result cache（如下皆是server result cache内容）。说白了，result cache 就是为了缓存结果集的一块区域，主要是缓存sql 查询结果集以及pl/sql function结果集。

对于 result cache存在几个参数，如下：

result_cache_max_result              integer    
result_cache_max_size                big integer
result_cache_mode                    string      MANUAL（AUTO、FORCE)

1）、result_cache_max_result 表示对于单个的缓存结果占整个result cache 大小的百分比。

2）、result_cache_max_size 参数用于设置该result cache 的大小，是一个动态参数，该参数为0 则说明result cache 功能禁用了。

3）、result_cache_mode，表示result cache的模式，其中有manual、force。manual 表示只有使用hints（result_cache）才可以对其结果进行缓存且当从result cache中获取结果集的时候也必须使用hints（result cache）参数；force表示强制对结果集进行缓存 oracle对该参数的设置不建议，如下：

FORCE mode is not recommended because the database and clients will attempt to cache all queries, which may create significant performance and latching overhead. Moreover, because queries that call non-deterministic PL/SQL functions are also cached, enabling the result cache in such a broad-based manner may cause material changes to the results.

如果需要不对操作进行缓存可以使用hints（no_result_cache)进行设置。

如下是练习过程：

一、

设置result cache 大小为20M，模式为manual，每个结果集占用总的cache比例为50%（为了测试方便）；

SQL> alter system set result_cache_mode=manual;

System altered.

SQL> alter system set  result_cache_max_result=50;

System altered.

SQL> show parameter result_cache

NAME                                 TYPE        VALUE

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

client_result_cache_lag              big integer 3000

client_result_cache_size             big integer 0

result_cache_max_result              integer     50

result_cache_max_size                big integer 20M

result_cache_mode                    string      MANUAL

result_cache_remote_expiration       integer     0

SQL>

那么启用result cache 与不启用的效果在那呢？如下测试见证分晓！

eg：

SQL> set autotrace trace

SQL> select count(*) from rhys.amy;

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation          | Name | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT   |      |     1 |   348   (1)| 00:00:05 |

|   1 |  SORT AGGREGATE    |      |     1 |            |          |

|   2 |   TABLE ACCESS FULL| AMY  | 87260 |   348   (1)| 00:00:05 |

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

Statistics

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

         61  recursive calls

          0  db block gets

       1271  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          5  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> r

  1* select count(*) from rhys.amy

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation          | Name | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT   |      |     1 |   348   (1)| 00:00:05 |

|   1 |  SORT AGGREGATE    |      |     1 |            |          |

|   2 |   TABLE ACCESS FULL| AMY  | 87260 |   348   (1)| 00:00:05 |

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

Statistics

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

          0  recursive calls

          0  db block gets

       1248  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> r

  1* select count(*) from rhys.amy

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation          | Name | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT   |      |     1 |   348   (1)| 00:00:05 |

|   1 |  SORT AGGREGATE    |      |     1 |            |          |

|   2 |   TABLE ACCESS FULL| AMY  | 87260 |   348   (1)| 00:00:05 |

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

Statistics

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

          0  recursive calls

          0  db block gets

       1248  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> SQL>

SQL>

首先看到查看rhys下的amy这张表在稳定下来的时候一致性读为1248，物理读为1246（万源之恶）。

现在使用result cache 功能。

SQL> select /*+result_cache*/ count(*) from rhys.amy;

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select /*+result_cache*/ count(*) from rhys.amy"

Statistics

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

          0  recursive calls

          0  db block gets

       1248  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

第一次执行该语句并将其缓存到result cache中，一致性读以及物理 读没有变化。

如下使用hints（result_cache）进行在此查询该结果集。如下：

SQL> select /*+result_cache*/ count(*) from rhys.amy;

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select /*+result_cache*/ count(*) from rhys.amy"

Statistics

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

          0  recursive calls

          0  db block gets

          0  consistent gets

          0  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL>

可见物理读和一致性读都没有了，直接获得了结果集。这是好事啊。呵呵。

对于mode为force模式演示如下：

SQL> alter system set result_cache_mode=force;

System altered.

SQL>

SQL> set autotrace trace

SQL> select count(*) from rhys.amy;

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select count(*) from rhys.amy"

Statistics

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

         63  recursive calls

          8  db block gets

       1327  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

         10  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> r

  1* select count(*) from rhys.amy

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select count(*) from rhys.amy"

Statistics

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

          0  recursive calls

          0  db block gets

          0  consistent gets

          0  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL>

另外在联机手册中并没提及到result_cache_mode 存在auto模式，但是我在不经意输错的是否发现了这个值。

SQL> alter system set result_cache_mode=false;
alter system set result_cache_mode=false
*
ERROR at line 1:
ORA-00096: invalid value FALSE for parameter result_cache_mode, must be from among FORCE, MANUAL, AUTO

查看资料发现auto，是只有使用hints的时候才能起作用，但是当再次查询结果的时候没必要在使用hints了，而是直接把结果取出来。测试如下：

SQL> set autotrace off

SQL> execute dbms_result_cache.flush;

PL/SQL procedure successfully completed.

SQL> alter system set result_cache_mode=auto;

System altered.

SQL> set autotrace trace

SQL> select /*+result_cache*/ count(*) from rhys.amy;

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select /*+result_cache*/ count(*) from rhys.amy"

Statistics

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

         49  recursive calls

          0  db block gets

       1275  consistent gets

       1246  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          5  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> r

  1* select /*+result_cache*/ count(*) from rhys.amy

Execution Plan

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

Plan hash value: 2204613761

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

| Id  | Operation           | Name                       | Rows  | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT    |                            |     1 |   348   (1)| 00:00:05 |

|   1 |  RESULT CACHE       | 6tux55tbcpqfj66980yb24pfbh |       |            |          |

|   2 |   SORT AGGREGATE    |                            |     1 |            |          |

|   3 |    TABLE ACCESS FULL| AMY                        | 87260 |   348   (1)| 00:00:05 |

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

Result Cache Information (identified by operation id):

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

   1 - column-count=1; dependencies=(RHYS.AMY); attributes=(single-row); name="select /*+result_cache*/ count(*) from rhys.amy"

Statistics

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

          0  recursive calls

          0  db block gets

          0  consistent gets

          0  physical reads

          0  redo size

        528  bytes sent via SQL*Net to client

        523  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

二、

result cache 管理

对于11g中新增了result cache 那么也新增了4个视图以及一个包。

相关视图如下：

  • v$result_cache_dependency
  • v$result_cache_memory
  • v$result_cache_objects
  • v$result_cache_statistics

    就不在介绍了，可以参考联机手册进行分析以及学习：

    http://www.oracle.com/pls/db112/search?word=v$result_cache_

    现在看一个dbms_result_cache包：

    存在有6个subprograms，

    Subprogram Description

    BYPASS Procedure

    Sets the bypass mode for the Result Cache

    FLUSH Function & Procedure

    Attempts to remove all the objects from the Result Cache, and depending on the arguments retains or releases the memory and retains or clears the statistics

    INVALIDATE Functions & Procedures

    Invalidates all the result-set objects that dependent upon the specified dependency object

    INVALIDATE_OBJECT Functions & Procedures

    Invalidates the specified result-set object(s)

    MEMORY_REPORT Procedure

    Produces the memory usage report for the Result Cache

    STATUS Function

    Checks the status of the Result Cache

    演示二个：

    其他参考：

    http://docs.oracle.com/cd/E11882_01/appdev.112/e40758/d_result_cache.htm#CHDJCFJG

    SQL> set serveroutput on
    
SQL> execute 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  = 20M bytes (20K blocks)
    
Maximum Result Size = 10M bytes (10K blocks)
    
[Memory]
    
Total Memory = 168264 bytes [0.134% of the Shared Pool]
    
... Fixed Memory = 5352 bytes [0.004% of the Shared Pool]
    
... Dynamic Memory = 162912 bytes [0.129% of the Shared Pool]
    
....... Overhead = 130144 bytes
    
....... Cache Memory = 32K bytes (32 blocks)
    
........... Unused Memory = 30 blocks
    
........... Used Memory = 2 blocks
    
............... Dependencies = 1 blocks (1 count)
    
............... Results = 1 blocks
    
................... SQL     = 1 blocks (1 count)

PL/SQL procedure successfully completed.

SQL> execute dbms_result_cache.memory_report(true);
    
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  = 20M bytes (20K blocks)
    
Maximum Result Size = 10M bytes (10K blocks)
    
[Memory]
    
Total Memory = 168264 bytes [0.134% of the Shared Pool]
    
... Fixed Memory = 5352 bytes [0.004% of the Shared Pool]
    
....... Memory Mgr = 200 bytes
    
....... Cache Mgr  = 208 bytes
    
....... Bloom Fltr = 2K bytes
    
....... State Objs = 2896 bytes
    
... Dynamic Memory = 162912 bytes [0.129% of the Shared Pool]
    
....... Overhead = 130144 bytes
    
........... Hash Table    = 64K bytes (4K buckets)
    
........... Chunk Ptrs    = 24K bytes (3K slots)
    
........... Chunk Maps    = 12K bytes
    
........... Miscellaneous = 130144 bytes
    
....... Cache Memory = 32K bytes (32 blocks)
    
........... Unused Memory = 30 blocks
    
........... Used Memory = 2 blocks
    
............... Dependencies = 1 blocks (1 count)
    
............... Results = 1 blocks
    
................... SQL     = 1 blocks (1 count)

PL/SQL procedure successfully completed.

    SQL> execute dbms_result_cache.flush;

PL/SQL procedure successfully completed.

SQL> execute dbms_result_cache.memory_report(true);
    
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 = 5352 bytes [0.004% of the Shared Pool]
    
... Fixed Memory = 5352 bytes [0.004% of the Shared Pool]
    
....... Memory Mgr = 200 bytes
    
....... Cache Mgr  = 208 bytes
    
....... Bloom Fltr = 2K bytes
    
....... State Objs = 2896 bytes
    
... Dynamic Memory = 0 bytes [0.000% of the Shared Pool]

PL/SQL procedure successfully completed.

SQL>

oracle 11g 之 result cache的更多相关文章

  1. [20190214]11g Query Result Cache RC Latches补充.txt

    [20190214]11g Query Result Cache RC Latches补充.txt --//上午测试链接:http://blog.itpub.net/267265/viewspace- ...

  2. [20190214]11g Query Result Cache RC Latches.txt

    [20190214]11g Query Result Cache RC Latches.txt --//昨天我重复链接http://www.pythian.com/blog/oracle-11g-qu ...

  3. Oracle 11g新特性

    文章转自网络 Oracle 11g于2007年7月11日美国东部时间11时(北京时间11日22时)正式发布,11g是甲骨文公司30年来发布的最重要的数据库版本,根据用户的需求实现了信息生命周期管理(I ...

  4. 11G新特性 -- Result Cache

    共享池存放sql语句的解析和编译版本,以便数据库能快速执行频繁执行的sql语句和plsql. 在11g中,数据库使用result cache来存放sql和plsql的执行结果. result cach ...

  5. Oracle 11g OCM 考试大纲

    考试大纲共分9部分.   一.Server Configuration 服务器配置 1  Create the database 创建数据库 2  Determine and set sizing p ...

  6. Oracle 11g Articles

    发现一个比较有意思的网站,http://www.oracle-base.com/articles/11g/articles-11g.php Oracle 11g Articles Oracle Dat ...

  7. Oracle 11g后台进程一览表

    Background Processes Table F-1 describes Oracle Database background processes. In this context, a ba ...

  8. orace result cache解析

      (1)   orace 11.2.0.4 在RAC数据库Dataguard切换时,出现少量数据丢失:          解决方案:关闭result cache 功能 或升级数据库版本并安装补丁: ...

  9. RHEL6.4 + Oracle 11g DG测试环境快速搭建参考

    环境现状: 两台虚拟主机A和B: 1. A机器已安装ASM存储的Oracle 11g 实例      参考:http://www.cnblogs.com/jyzhao/p/4332410.html 2 ...

随机推荐

  1. ios程序开发杂记

    ios程序开发杂记 一.程序构建 与一般的程序构建无太大区别,都是源文件编译链接这一套,通常是在mac上做交叉编译,也就是利用xcode里带的ios编译工具集去生成arm架构的ios程序(或是x86的 ...

  2. Android消息推送完美解决方案全析

    推送功能在手机应用开发中越来越重要,已经成为手机开发的必须.在Android应用开发中,由于众所周知的原因,Android消息推送我们不得不大费周折.本文就是用来和大家共同探讨一种Android消息推 ...

  3. 高斯消元与xor方程组

    ;i<=n;i++) { ;j<=n;j++) if(a[j]>a[i]) swap(a[i],a[j]); if(!a[i]) break; ;j>=;j--) ) { ;k ...

  4. 使用Java VisualVM监控远程JVM

    我们经常需要对我们的开发的软件做各种测试, 软件对系统资源的使用情况更是不可少, 目前有多个监控工具, 相比JProfiler对系统资源尤其是内存的消耗是非常庞大,JDK1.6开始自带的VisualV ...

  5. 纯css做的安卓开机动画

    随着css3的发展,越来越多的负责绚丽的效果可以由纯css来完成了.用css3实现的动画效果丝毫不必js实现的逊色,而且浏览器对css渲染的速度远比js快,大多数时候css的体积也不js小.其中css ...

  6. I.MX6 Ubuntu core porting

    /*********************************************************************** * I.MX6 Ubuntu core porting ...

  7. acdream 1210 Chinese Girls' Amusement (打表找规律)

    题意:有n个女孩围成一个圈从第1号女孩开始有一个球,可以往编号大的抛去(像传绣球一样绕着环来传),每次必须抛给左边第k个人,比如1号会抛给1+k号女孩.给出女孩的人数,如果他们都每个人都想要碰到球一次 ...

  8. ffmpeg显示视频

    项目最近需要实现播放视频功能,这个在上家公司就做过.虽然跟之前的场景不一样,有以前的功底还是很快可以解决,事实也确实如此.在使用DShow处理完视频分割与合并后,继续使用DShow显示视频,很快即完成 ...

  9. tomcat调优的几个方面

    转载自:http://my.oschina.net/u/593721/blog/146710 作者:小报童 和早期版本相比最新的Tomcat提供更好的性能和稳定性.所以一直使用最新的Tomcat版本. ...

  10. z-index的妙用

    总是在纠结一个问题,当然我是前端初学者.这个问题就是,一个元素放在另一个元素里面,总希望它显示时,但是别撑开元素.这个时候一定要想到z-index. 例如今天写的一个浮动在导航栏下面的一个图片,我用的 ...