引數 optimizer_index_cost_adj

SQL>  show  parameter  index;

 

NAME                                                                  TYPE                VALUE

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

optimizer_index_caching                            integer          0

optimizer_index_cost_adj                          integer          100

skip_unusable_indexes                                boolean          TRUE

 

 

optimizer_index_cost_adj取值0-1000，預設100  ;值越小oracle就越趨向使用索引

 

 

在節點1上執行：

SQL>  alter  system  set  optimizer_index_cost_adj=35  scope=both;

SQL>  show  parameter  ind;

 

NAME                                                                  TYPE                VALUE

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

optimizer_index_caching                            integer          0

optimizer_index_cost_adj                          integer          35

skip_unusable_indexes                                boolean          TRUE

use_indirect_data_buffers                        boolean          FALSE

 

 

然後在2節點上檢視：

SQL>  show  parameter  ind;

 

NAME                                                                  TYPE                VALUE

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

optimizer_index_caching                            integer          0

optimizer_index_cost_adj                          integer          35

skip_unusable_indexes                                boolean          TRUE

use_indirect_data_buffers                        boolean          FALSE

 

 

scope=both        是指在當前記憶體中和spfile都改了

scope=spfile    是指只改了spfile，重啟生效

 

一般oltp庫上都是10-50左右