_disable_logging对于性能的影响

设置了_disable_logging参数,可以禁用日志的生成,从而提高某些测试的性能. 以下测试,纯属测试目的,其他内容请参考本站其他文章: http://www.eygle.com/archives/2006/04/more_about_disable_logging.Html 禁用日志情况下: SQL> connect / as sysdba
Connected.
SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracle instance shut down.
SQL> startup
ORACLE instance started. Total System Global Area 286755168 bytes
Fixed Size                   731488 bytes
Variable Size             167772160 bytes
Database Buffers          117440512 bytes
Redo Buffers                 811008 bytes
Database mounted.
Database opened.
SQL> connect eygle/eygle
Connected.
SQL> show parameter disable NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
_disable_logging                     boolean     TRUE 测试创建100万数据表: SQL> create table test as select * from dba_objects where 1=0; Table created. SQL> set timing on
SQL> begin
2 for i in 1 .. 10000 loop
3 insert into test select * from dba_objects where rownum < 101;
4 commit;
5 end loop;
6 end;
7 / PL/SQL procedure sUCcessfully completed. Elapsed: 00:00:40.46
SQL> truncate table test; Table truncated. Elapsed: 00:00:52.72 大约时间用了40秒. 再看正常日志生成下: SQL> connect / as sysdba
Connected.
SQL> alter system set "_disable_logging"=false; System altered. Elapsed: 00:00:00.05
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started. Total System Global Area 286755168 bytes
Fixed Size                   731488 bytes
Variable Size             167772160 bytes
Database Buffers          117440512 bytes
Redo Buffers                 811008 bytes
Database mounted.
Database opened.
SQL> show parameter disable
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
_disable_logging                     boolean     FALSE

SQL> connect eygle/eygle
Connected.
SQL> set timing on
SQL>
SQL> begin
2    for i in 1 .. 10000 loop
3   insert into test select * from dba_objects where rownum < 101;
4 commit;
5    end loop;
6 end;
7 /   PL/SQL procedure successfully completed. Elapsed: 00:01:54.04
SQL>
SQL> truncate table test; Table truncated. Elapsed: 00:01:01.56 此时大约用时1分54秒. 两者差距为: 114 / 40 = 2.85 倍. 我们可以看出两者的差距是显著的.不作过多测试了,就此打住.大家有爱好的可以自己测试一下. 以上测试的环境为: SQL> select * from v$version; BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
PL/SQL Release 9.2.0.4.0 - Production
CORE    9.2.0.3.0       Production
TNS for Solaris: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production
原文地址：http://www.eygle.com/archives/2006/04/disable_logging_performance.html