本文详细对比了Oracle数据库在非归档模式和归档模式下，通过不同批量插入方式对redo日志的影响，并提供了优化建议。主要分为三部分：非归档模式下通过insert/*+append*/into方式减少redo产生；归档模式下设置表的logging属性为false以减少redo；最后对比了在归档模式下几种批量插入操作的效率。优化建议包括设置表为nologging状态，以降低redo日志的生成，提高批量数据加载性能。
一 非归档模式下
D:>sqlplus "/ as sysdba"
数据库版本为9.2.0.1.0
SQL*Plus: Release 9.2.0.1.0 - Production on 星期一 8月 14 10:20:39 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
连接到:
Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.1.0 - Production
当前session产生的redo
SQL> create or replace view redo_size
2 as
3 select value
4 from v$mystat, v$statname
5 where v$mystat.statistic# = v$statname.statistic#
6 and v$statname.name = 'redo size';
视图已建立。
授权给相应数据库schema
SQL> grant select on redo_size to liyong;
授权成功。
SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。
SQL> startup mount;
ORACLE 例程已经启动。
Total System Global Area 122755896 bytes
Fixed Size 453432 bytes
Variable Size 88080384 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
数据库装载完毕。
非归档模式
SQL> alter database noarchivelog;
数据库已更改。
SQL> alter database open;
数据库已更改。
SQL> create table redo_test as
2 select * from all_objects where 1=2;
表已创建。
SQL> select * from sys.redo_size;
VALUE
----------
59488
SQL> insert into redo_test
2 select * from all_objects;
已创建28260行。
SQL> select * from sys.redo_size;
VALUE
----------
3446080
SQL> insert /*+ append */ into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
3458156
可以看到insert /*+ append */ into方式redo产生很少.
SQL> select 3446080-59488,3458156-3446080 from dual;
3446080-59488 3458156-3446080
------------- ---------------
3386592 12076
将表redo_test置为nologging状态.
SQL> alter table redo_test nologging;
表已更改。
SQL> select * from sys.redo_size;
VALUE
----------
3460052
SQL> insert into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
6805876
SQL> insert /*+ append */ into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
6818144
非归档模式下表的nologging状态对于redo影响不大
SQL> select 6805876-3460052,6818144-6805876 from dual;
6805876-3460052 6818144-6805876
--------------- ---------------
3345824 12268
结论: 在非归档模式下通过insert /*+ append */ into方式批量加载数据可以大大减少redo产生.
二 归档模式下
SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。
SQL> startup mount;
ORACLE 例程已经启动。
Total System Global Area 122755896 bytes
Fixed Size 453432 bytes
Variable Size 88080384 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
数据库装载完毕。
SQL> alter database archivelog;
数据库已更改。
SQL> alter database open;
数据库已更改。
SQL> conn liyong
请输入口令:
已连接。
将表redo_test重新置为logging
SQL> alter table redo_test logging;
表已更改。
SQL> select * from sys.redo_size;
VALUE
----------
5172
SQL> insert into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
3351344
SQL> insert /*+ append */ into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
6659932
可以看到在归档模式下，且表的logging属性为true,insert /*+ append */ into这种方式也会纪录大量redo
SQL> select 3351344-5172,6659932-3351344 from dual;
3351344-5172 6659932-3351344
------------ ---------------
3346172 3308588
将表置为nologging
SQL> alter table redo_test nologging;
表已更改。
SQL> select * from sys.redo_size;
VALUE
----------
6661820
SQL> insert into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
10008060
SQL> insert /*+ append */ into redo_test
2 select * from all_objects;
已创建28260行。
SQL> commit;
提交完成。
SQL> select * from sys.redo_size;
VALUE
----------
10022852
可以发现在归档模式，要设置表的logging属性为false，才能通过insert /*+ append */ into大大减少redo产生.
SQL> select 10008060-6661820,10022852-10008060 from dual;
10008060-6661820 10022852-10008060
---------------- -----------------
3346240 14792
结论: 在归档模式下,要设置表的logging属性为false，
才能通过insert /*+ append */ into大大减少redo.
三 下面我们再看一下在归档模式下，几种批量insert操作的效率对比.
redo_test表有45W条记录
SQL> select count(*) from redo_test;
COUNT(*)
----------
452160
1 最常见的批量数据加载 25秒
SQL> create table insert_normal as
2 select * from redo_test where 0=2;
表已创建。
SQL> set timing on
SQL> insert into insert_normal
2 select * from redo_test;
已创建452160行。
提交完成。
已用时间: 00: 00: 25.00
2 使用insert /*+ append */ into方式(这个的原理可以参见<<批量DML操作优化建议.txt>>)，但纪录redo. 17.07秒
SQL> create table insert_hwt
2 as
3 select * from redo_test where 0=2;
表已创建。
SQL> insert /*+ append */ into insert_hwt
2 select * from redo_test;
已创建452160行。
提交完成。
已用时间: 00: 00: 17.07
3 使用insert /*+ append */ into方式，且通过设置表nologging不纪录redo.
SQL> create table insert_hwt_with_nologging nologging
2 as
3 select * from redo_test where 2=0;
表已创建。
/*
或者通过
alter table table_name nologging设置
*/
SQL> insert /*+ append */ into insert_hwt_with_nologging 11.03秒
2 select * from redo_test;
已创建452160行。
提交完成。
已用时间: 00: 00: 11.03
总结:
我们看到对于批量操作，如果设置表nologging，可以大大提高性能.原因就是Oracle没有纪录DML所产生的redo.
当然，这样会影响到备份。nologging加载数据后要做数据库全备.
re: Oracle的Nologging何时生效 与 批量insert加载数据速度(zt)
下面我又试了试insert into XXX values (XXX)能不能少产生redo,做了试验发现,不行的,下面的过程.
SQL> select * from v$version where rownum archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 17
Current log sequence 19
SQL> create or replace view redo_size
2 as
3 select value
4 from v$mystat, v$statname
5 where v$mystat.statistic# = v$statname.statistic#
6 and v$statname.name = 'redo size';
View created.
SQL> grant select on redo_size to ljg;
SQL> conn ljg/ljg
Connected.
SQL> create table redo_test as
2 select * from all_objects where 1=2;
SQL> CREATE OR REPLACE PROCEDURE p_loging
2 as
3 CURSOR c_a IS
4 SELECT * FROM all_objects;
5
6 BEGIN
7 FOR x IN c_a LOOP
8 INSERT INTO REDO_TEST
9 VALUES(x.OWNER, x.OBJECT_NAME, x.SUBOBJECT_NAME, x.OBJECT_ID, x.DATA_OBJE CT_ID,
10 x.OBJECT_TYPE, x.CREATED, x.LAST_DDL_TIME, x.TIMESTAMP, x.STATUS, x.TEMPORARY, x.GENERATED, x.SECONDARY);
11 END LOOP;
12 COMMIT;
13
14 END;
15 /
Procedure created.
SQL> CREATE OR REPLACE PROCEDURE p_nologing
2 as
3 CURSOR c_a IS
4 SELECT * FROM all_objects;
5
6 BEGIN
7 FOR x IN c_a LOOP
8 INSERT /*+ APPEND */ INTO REDO_TEST
9 VALUES(x.OWNER, x.OBJECT_NAME, x.SUBOBJECT_NAME, x.OBJECT_ID, x.DATA_OBJECT_ID,
10 x.OBJECT_TYPE, x.CREATED, x.LAST_DDL_TIME, x.TIMESTAMP, x.STATUS, x.TEMPORARY, x.GENERATED, x.SECONDARY);
11 END LOOP;
12 COMMIT;
13
14 END;
15 /
Procedure created.
SQL> select * from sys.redo_size;
VALUE
----------
85940
SQL> exec p_loging;
PL/SQL procedure successfully completed.
SQL> select * from sys.redo_size;
VALUE
----------
15273968
SQL> exec p_nologing;
PL/SQL procedure successfully completed.
SQL> select * from sys.redo_size;
VALUE
----------
30411272
SQL> select 15273968- 85940 logging,30411272-15273968 nologging from dual;
LOGGING NOLOGGING
---------- ----------
15188028 15137304
可以看到nologging和logging产生的redo差不多.
re: Oracle的Nologging何时生效 与 批量insert加载数据速度(zt)
下面我又试了试insert into XXX values (XXX)能不能少产生redo,做了试验发现,不行的,下面的过程.
SQL> select * from v$version where rownum archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 17
Current log sequence 19
SQL> create or replace view redo_size
2 as
3 select value
4 from v$mystat, v$statname
5 where v$mystat.statistic# = v$statname.statistic#
6 and v$statname.name = 'redo size';
View created.
SQL> grant select on redo_size to ljg;
SQL> conn ljg/ljg
Connected.
SQL> create table redo_test as
2 select * from all_objects where 1=2;
SQL> CREATE OR REPLACE PROCEDURE p_loging
2 as
3 CURSOR c_a IS
4 SELECT * FROM all_objects;
5
6 BEGIN
7 FOR x IN c_a LOOP
8 INSERT INTO REDO_TEST
9 VALUES(x.OWNER, x.OBJECT_NAME, x.SUBOBJECT_NAME, x.OBJECT_ID, x.DATA_OBJE CT_ID,
10 x.OBJECT_TYPE, x.CREATED, x.LAST_DDL_TIME, x.TIMESTAMP, x.STATUS, x.TEMPORARY, x.GENERATED, x.SECONDARY);
11 END LOOP;
12 COMMIT;
13
14 END;
15 /
Procedure created.
SQL> CREATE OR REPLACE PROCEDURE p_nologing
2 as
3 CURSOR c_a IS
4 SELECT * FROM all_objects;
5
6 BEGIN
7 FOR x IN c_a LOOP
8 INSERT /*+ APPEND */ INTO REDO_TEST
9 VALUES(x.OWNER, x.OBJECT_NAME, x.SUBOBJECT_NAME, x.OBJECT_ID, x.DATA_OBJECT_ID,
10 x.OBJECT_TYPE, x.CREATED, x.LAST_DDL_TIME, x.TIMESTAMP, x.STATUS, x.TEMPORARY, x.GENERATED, x.SECONDARY);
11 END LOOP;
12 COMMIT;
13
14 END;
15 /
Procedure created.
SQL> select * from sys.redo_size;
VALUE
----------
85940
SQL> exec p_loging;
PL/SQL procedure successfully completed.
SQL> select * from sys.redo_size;
VALUE
----------
15273968
SQL> exec p_nologing;
PL/SQL procedure successfully completed.
SQL> select * from sys.redo_size;
VALUE
----------
30411272
SQL> select 15273968- 85940 logging,30411272-15273968 nologging from dual;
LOGGING NOLOGGING
---------- ----------
15188028 15137304
可以看到nologging和logging产生的redo差不多.
re: Oracle的Nologging何时生效 与 批量insert加载数据速度(zt)
在ITPUB中问到可以用BULK COLLECT 来减少insert into values的redo.
CREATE OR REPLACE PROCEDURE p_BulkAdd
AS
TYPE Tredo_test IS TABLE OF REDO_TEST%ROWTYPE;
V_REDO_TEST Tredo_test;
BEGIN
SELECT * BULK COLLECT INTO V_REDO_TEST FROM ALL_OBJECTS;
FORALL X IN V_REDO_TEST.FIRST..V_REDO_TEST.LAST
INSERT INTO REDO_TEST VALUES V_REDO_TEST(X);
END;
/
SQL> select * from sys.redo_size;
VALUE
----------
30411272
SQL> exec p_bulkadd;
PL/SQL procedure successfully completed.
SQL> select * from sys.redo_size;
VALUE
----------
35050796
SQL> select 35050796-30411272 from dual;
35050796-30411272
-----------------
4639524
这个做的确是少了很多redo.是一个方法.
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