(非归档模式下)创建表T01:
SQL> create table t01 as select * from dba_objects where 1=2;
Table created.
(非归档模式下)查看当前redo大小:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
49784
(非归档模式下)普通INSERT语句插入:
SQL> insert into t01 select * from dba_objects;
11698 rows created.
(非归档模式下)查看普通INSERT语句执行后,当前redo大小:
SQL> select value
from v$mystat,v$statname
2 3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘;
VALUE
----------
1305724
(非归档模式)采用HINT /*+ append*/执行INSERT语句:
SQL> insert /*+ append */ into t01 select * from dba_objects;
11698 rows created.
(非归档模式)查询带/*+ append*/的INSERT执行后,当前redo大小:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘;
VALUE
----------
1308140
(非归档模式)计算使用HINT(/*+ append*/)和普通INSERT语句分别产生的redo大小:
SQL> select (1308140-1305724) redo_append,(1305724-49784) redo from dual;
REDO_APPEND REDO
----------- ----------
2416 1255940
可见,在非归档模式下,INSERT语句采用HINT /*+ APPEND*/的方式确实比普通INSERT语句产生的redo要少很多。
=========================================
下面测试归档模式下
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/arch
Oldest online log sequence 109
Next log sequence to archive 111
Current log sequence 111
(归档模式)查看当前redo大小:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
19540
(归档模式)执行普通INSERT语句:
SQL> insert into t01 select * from dba_objects;
11698 rows created.
(归档模式)普通INSERT方式产生的redo大小:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
1218884
(归档模式)采用HINT /*+ append*/执行INSERT语句:
SQL> insert /*+ append */ into t01 select * from dba_objects;
11698 rows created.
(归档模式)查询带/*+ append*/的INSERT执行后,当前redo大小:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘;
VALUE
----------
2451664
(归档模式)计算使用HINT(/*+ append*/)和普通INSERT语句分别产生的redo大小:
SQL> select (2451664-1218884) redo_append,(1218884-19540) from dual;
REDO_APPEND (1218884-19540)
----------- ---------------
1232780 1199344
可见,在归档模式下,采用HINT与普通INSERT方式产生的redo量是相当的,且略大于普通INSERT语句产生的redo量。
=========================================
再看一种情况,归档模式,T01也是LOGGING模式
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
2541780
SQL> insert /*+ append nologging */ into t01 select * from dba_objects;
或者执行:
SQL> insert /*+ append */ into t01 nologging select * from dba_objects;
也将产生redo的量为:1233040。
=========================================
最后一种情况:
(归档模式)修改T01的属性为NOLOGGING:
SQL> alter table t01 nologging;
Table altered.
SQL> select table_name,logging from dba_tables where table_name=‘T01‘;
TABLE_NAME LOG
------------------------------ ---
T01 NO
(归档模式)查看当前redo值:
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
5010600
(归档模式)执行普通INSERT语句:
SQL> insert into t01 select * from dba_objects;
11698 rows created.
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
6209848
(归档模式)采用HINT /*+ append*/执行INSERT语句:
SQL> insert /*+ append */ into t01 select * from dba_objects;
11698 rows created.
SQL> select value
2 from v$mystat,v$statname
3 where v$mystat.statistic#=v$statname.statistic#
4 and v$statname.name=‘redo size‘
5 /
VALUE
----------
6210536
(归档模式)计算两者产生的redo差值:
SQL> select (6210536-6209848) redo_append,(6209848-5010600) redo from dual;
REDO_APPEND REDO
----------- ----------
688 1199248
可见,在归档模式下,将表调整为NOLOGGING,产生的redo量是最少的!
对比一下:
非归档,T01(LOGGING),普通INSERT语句产生的redo值:1255940
非归档,T01(LOGGING),HINT /*+append*/,产生的redo值:2416
归档,T01(LOGGING),普通INSERT语句产生的redo值:1199344
归档,T01(LOGGING), HINT /*+ append*/,产生的redo值:1232780
归档,T01(LOGGING),/*+append*/ + nologging,产生的redo值:1233040
归档,T01(NOLOGGING),普通INSERT语句产生的redo值:688
归档,T01(NOLOGGING),HINT /*+append*/,产生的redo值:1199248
综合以上的数据,可以明白,如果想INSERT语句执行的更快,产生更少的redo,分两种情况:
非归档模式:
1、在INSERT语句中使用HINT /*+ append */或者使用HINT /*+ append nologging */两者插入数据的速度相同,但是后者产生的日志要少10倍左右
归档模式:
1、将目标表修改为NOLOGGING(alter table xxx nologging),然后在INSERT语句中使用HINT /*+ append */.或者HINT /*+ append nologging */
2、append在没有使用nologging的情况下,并不会减少归档日志的产生。
3、将表改为nologging属性的情况下插入数据,几乎不会产生归档日志,但前提是必须要使用append参数,否则产生依然会产生归档日志,只不过表在创建时不会产生归档。