oracle优化器相关参数设置

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

With the Partitioning, Real Application Clusters, Automatic Storage Management,

OLAP,

Data Mining and Real Application Testing options

SQL> show parameter optimizer

NAME                                 TYPE        VALUE

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

optimizer_capture_sql_plan_baselines boolean     FALSE

optimizer_dynamic_sampling           integer     2

optimizer_features_enable            string      11.2.0.4

optimizer_index_caching              integer     0

optimizer_index_cost_adj             integer     100

optimizer_mode                               string      FIRST_ROWS_1000

optimizer_secure_view_merging      boolean     TRUE

optimizer_use_invisible_indexes      boolean     FALSE

optimizer_use_pending_statistics     boolean     FALSE

optimizer_use_sql_plan_baselines     boolean     TRUE

SQL>

SQL> col event for a30

SQL> select event,average_wait from v$system_event where event like '%db file%';

EVENT                          AVERAGE_WAIT

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

db file sequential read                 1.5

db file scattered read                 6.06

db file single write                    .89

db file parallel write                  .55

db file async I/O submit            0

db file parallel read                  8.86

6 rows selected.

SQL>

SQL> select 1.5/6.06 from dual;

1.5/6.06

----------

.247524752

---接近25% (全表扫描代价与执行单块的相对比例,默认值100)

SQL> alter system set optimizer_index_cost_adj=25 scope=both;

System altered.

SQL>

---索引在SGA被缓存化的百分比

SQL> alter system set optimizer_index_caching=40 scope=both;

System altered.

SQL>

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

select event,average_wait from v$system_event where event like '%db file%';

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

1：高水位的回收

alter table my_solgle enable row movement;

alter table my_solgle shrink space;

2:数据密度问题

alter tablespace TBS_INDEX_DATA_1 coalesce;

-----查询计划查看

SQL> set autotrace traceonly;

SQL> select count(1) from my_solgle;

Execution Plan

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

Plan hash value: 75121460

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

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

| Pstart| Pstop |

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

|   0 | SELECT STATEMENT          |                  |     1 |   120   (0)| 00:00:02 |       |       |

|   1 |  SORT AGGREGATE           |                  |     1 |            ||       |       |

|   2 |   PARTITION RANGE ALL     |                  |  4647K|   120   (0)| 00:00:02 |     1 |1048575|

|   3 |    BITMAP CONVERSION COUNT|                  |  4647K|   120   (0)| 00:00:02 |       |       |

|   4 |     BITMAP INDEX FULL SCAN| NIDX_OSA_IS_FJMM |       |            |     |     1 |1048575|

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

Statistics

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

605    recursive calls    --内部递归调用次数

0      db block gets        --请求的缓存数据块数

2265   consistent gets  --当前查询读的缓存块数

471    physical reads    --磁盘读取数据块数

0      redo size                --生成日志大小

349    bytes sent via SQL*Net to client

363    bytes received via SQL*Net from client

2      SQL*Net roundtrips to/from client   --SQL*Net通信收发次数统计

25     sorts (memory)                       --内存中排序大小

0      sorts (disk)                        ---磁盘中排序大小

1      rows processed