在归档模式和非归档模式下，设定表为logging和nologging，测量普通的insert 和insert /*+append*/生成redo大小。第一次测试我对下列结果报怀疑态度，于是又重新测试一遍，结果差不多，想想是测试的数量太少。如果是在正式环境上做数据迁移，最好就选择最后一种模式。

1.非归档模式

sql> create view m_redo as
  2   select  value
  3   from v$sysstat,v$statname
  4  where v$sysstat.statistic# =v$statname.statistic#
  5     and v$statname.name ='redo size';
sql> create table test as select * from dba_objects where 1=0;

1.1表为logging

sql> select * from  m_redo;
     VALUE
----------
   9236752
sql> insert into test select * from dba_objects;

已创建50325行。

sql> commit;
 
sql> select * from  m_redo;
     VALUE
----------
  14943076
sql> select (14943076-9236752)/1024/1024||'M' from dual;
(14943076-9236752)/10
---------------------
5.441974639892578125M
sql> truncate table test;
sql> select * from  m_redo;
     VALUE
----------
  15048424
sql> insert /*+append*/  into test select * from dba_objects;

sql> commit;
sql> select * from  m_redo;
     VALUE
----------
  15136764
sql> select (15136764-15048424)/1024/1024||'M' from dual;
(15136764-15048424)/
--------------------
.084247589111328125M

1.2表为nologging

sql> truncate table test;
sql> alter table test nologging;
sql> select * from  m_redo;
     VALUE
----------
  15190864
sql> insert into test select * from dba_objects;

sql> commit;
sql> select * from  m_redo;
     VALUE
----------
  20876728
sql> select (20876728-15190864)/1024/1024||'M' from dual;
(20876728-15190864)/
--------------------
5.42246246337890625M
sql> truncate table test;
sql> select * from  m_redo;
     VALUE
----------
  20937256
sql> insert /*+append*/  into test select * from dba_objects;
已创建50325行。
sql> commit;
sql> select * from  m_redo;
     VALUE
----------
  21000604
sql> select (21000604-20937256)/1024/1024||'M' from dual;
(21000604-20937256)/
--------------------
.060413360595703125M

2.归档模式

在重新开一个session

sql> conn test/test

已连接。

sql>shutdown immediate
sql>startup mount
sql>alter database archivelog
sql> alter database open;

数据库已更改。

sql> truncate table test;

表被截断。

sql> select * from m_redo;
    VALUE
----------
   130848
sql> insert into test select * from dba_objects;

已创建50325行。

sql> commit;
sql> select * from m_redo;
    VALUE
----------
  5817044
sql> select (5817044-130848)/1024/1024||'M' from dual;
(5817044-130848)/1024
---------------------
5.422779083251953125M
sql> truncate table test;
sql> select * from m_redo;
    VALUE
----------
  5879644
sql> insert /*+append*/ into test select * from dba_objects;

sql> commit;
sql> select * from m_redo;
    VALUE
----------
  5943068
sql> select (5943068-5879644)/1024/1024||'M' from dual;
(5943068-5879644
----------------
.06048583984375M

sql> truncate table test;
sql> alter table test nologging;

表已更改。

sql> select * from m_redo;
    VALUE
----------
  5990988
sql> insert into test select * from dba_objects;

sql> commit;
sql> select * from m_redo;
    VALUE
----------
  11676352
sql> select (11676352-5990988)/1024/1024||'M' from dual;
(11676352-5990988)/10
---------------------
5.421985626220703125M
sql> truncate table test;。
sql> select * from m_redo;
    VALUE
----------
  11736328
sql> insert /*+append*/ into test select * from dba_objects;

sql> commit;
sql> select * from m_redo;
    VALUE
----------
  11799676
sql> select (11799676-11736328)/1024/1024||'M' from dual;
(11799676-11736328)/
--------------------
.060413360595703125M