對錶進行dml操作時影響產生日誌量的幾個因素

歸檔模式
SQL> archive log list;
Database log mode           Archive Mode
Automatic archival           Enabled
Archive destination           /u02/archive_log
Oldest online log sequence     29
Next log sequence to archive   31
Current log sequence           31
1.創建測試表hat_objects
SQL> create table hat_objects as select * from all_objects where 1<>1;
 
Table created

2.打開執行計劃
SQL> set autotrace traceonly statistics;
3.插入數據
SQL> insert into hat_objects select * from all_objects;

40685 rows created.


Statistics
----------------------------------------------------------
       5877  recursive calls
       5779  db block gets
      80216  consistent gets
      0  physical reads
    4684152  redo size
    675  bytes sent via SQL*Net to client
    585  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      2  sorts (memory)
      0  sorts (disk)
      40685  rows processed

4.使用提示插入數據
SQL> insert /*+ append */ into hat_objects select * from all_objects;

40685 rows created.


Statistics
----------------------------------------------------------
       5278  recursive calls
    774  db block gets
      79281  consistent gets
      0  physical reads
    4692132  redo size
    660  bytes sent via SQL*Net to client
    599  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      1  sorts (memory)
      0  sorts (disk)
      40685  rows processed

注：直接insert與使用append提示insert產生的日誌大小相差無幾，未減少日誌的產生。

5.設置hat_objects爲nologging模式
SQL> alter table hat_objects nologging;

Table altered.

6.插入數據
SQL> insert into hat_objects select * from all_objects;

40685 rows created.


Statistics
----------------------------------------------------------
       5232  recursive calls
       5104  db block gets
      80000  consistent gets
      0  physical reads
    4630652  redo size
    676  bytes sent via SQL*Net to client
    585  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      2  sorts (memory)
      0  sorts (disk)
      40685  rows processed

7.使用提示插入數據
SQL> insert /*+ append */ into hat_objects select * from all_objects;

40685 rows created.


Statistics
----------------------------------------------------------
       5278  recursive calls
    776  db block gets
      79281  consistent gets
      0  physical reads
      19648  redo size
    662  bytes sent via SQL*Net to client
    599  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      1  sorts (memory)
      0  sorts (disk)
      40685  rows processed

注：當表hat_objects設置爲nologging模式後，使用append提示後insert，日誌的產生量明顯比直接

insert少。

非歸檔模式
SQL> archive log list;
Database log mode           No Archive Mode
Automatic archival           Disabled
Archive destination           /u02/archive_log
Oldest online log sequence     29
Current log sequence           31
1.創建測試表
SQL> create table hat_objects as select * from all_objects where 1<>1;

Table created.

2.插入數據
SQL> insert into hat_objects select * from all_objects;

40685 rows created.


Statistics
----------------------------------------------------------
       6773  recursive calls
       6276  db block gets
      80723  consistent gets
      2  physical reads
    4737072  redo size
    680  bytes sent via SQL*Net to client
    585  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
     21  sorts (memory)
      0  sorts (disk)
      40685  rows processed

3.使用提示插入數據
SQL> insert /*+ append */ into hat_objects select * from all_objects;

40684 rows created.


Statistics
----------------------------------------------------------
       5278  recursive calls
    762  db block gets
      79281  consistent gets
      0  physical reads
      18332  redo size
    664  bytes sent via SQL*Net to client
    599  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      1  sorts (memory)
      0  sorts (disk)
      40684  rows processed

注：直接insert與使用append提示insert產生的日誌大小相差很大，減少了日誌的產生。

4.設置表hat_objects爲nologging模式
SQL> alter table hat_objects nologging;

Table altered.

5.插入數據
SQL> insert into hat_objects select * from all_objects;

40684 rows created.


Statistics
----------------------------------------------------------
       5454  recursive calls
       5104  db block gets
      80005  consistent gets
      0  physical reads
    4630688  redo size
    680  bytes sent via SQL*Net to client
    585  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      6  sorts (memory)
      0  sorts (disk)
      40684  rows processed

6.使用提示插入數據
SQL> insert/*+ append */ into hat_objects select * from all_objects;

40684 rows created.


Statistics
----------------------------------------------------------
       5278  recursive calls
    782  db block gets
      79281  consistent gets
      0  physical reads
      19648  redo size
    664  bytes sent via SQL*Net to client
    598  bytes received via SQL*Net from client
      4  SQL*Net roundtrips to/from client
      1  sorts (memory)
      0  sorts (disk)
      40684  rows processed

注：當表hat_objects設置爲nologging模式後，使用append提示後insert，日誌量比直接insert少，

但與表hat_objects設置爲logging模式相比較，同樣使用append提示產生的日誌量差不多。

總結：在歸檔模式下，只有將表設置爲nologging並且使用append提示才能大量減少日誌的產生；在非

歸檔模式下，無論是否將表設置爲nologging，只要使用append提示都會大量減少日誌的產生。