[20170515]参数fast_start_mttr_target

[20170515]fast_start_mttr_target容易混淆的地方.txt

--//自己很少关注这个参数.但是确实非常容易混淆.

1.环境:

SYS@book> @ &r/ver1

PORT_STRING         VERSION    BANNER

------------------- ---------- --------------------------------------------------------------------------------

x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

--//如果不设置,也是缺省设置.

$ strings spfilebook.ora | grep -i fast_start_mttr_target

SYS@book> show spparameter fast_start_mttr_targ

SID      NAME                          TYPE    VALUE

-------- ----------------------------- ------- -------

*        fast_start_mttr_target        integer

SYS@book> show parameter fast_start_mttr_targ

NAME                   TYPE    VALUE

---------------------- ------- ------

fast_start_mttr_target integer 0

--//alert*.log:

Successful open of redo thread 1

MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set

SYS@book> select WRITES_AUTOTUNE from v$instance_recovery ;

WRITES_AUTOTUNE

---------------

             52

--//实际上这个时候是开启自动调整.

--//如果你设置0,自动关闭这个功能.

2.设置fast_start_mttr_target=0;

SYS@book> alter system set fast_start_mttr_target=0;

System altered.

SYS@book> shutdown immediate ;

Database closed.

Database dismounted.

ORACLE instance shut down.

SYS@book> startup

ORACLE instance started.

Total System Global Area  634732544 bytes

Fixed Size                  2255792 bytes

Variable Size             197133392 bytes

Database Buffers          427819008 bytes

Redo Buffers                7524352 bytes

Database mounted.

Database opened.

Mon May 15 10:40:15 2017

ARC0 started with pid=22, OS id=34420

ARC0: Archival started

LGWR: STARTING ARCH PROCESSES COMPLETE

ARC0: STARTING ARCH PROCESSES

Thread 1 opened at log sequence 745

  Current log# 3 seq# 745 mem# 0: /mnt/ramdisk/book/redo03.log

--//提示一样,但是现在是关闭的.

---------------------- ------- -----

SID      NAME                   TYPE    VALUE

-------- ---------------------- ------- ------

*        fast_start_mttr_target integer 0

--//你等很久观察,这是WRITES_AUTOTUNE一直是0.

3.设置fast_start_mttr_target=200:

SYS@book> alter system set fast_start_mttr_target=200;

--//重启:

fast_start_mttr_target integer 200

-------- ---------------------- ------- -----

*        fast_start_mttr_target integer 200

--//alert没有mttr的相关显示,表示已经MTTR advisory is enabled.