[20170515]參數fast_start_mttr_target

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

--//自己很少關注這個參數.但是确實非常容易混淆.

1.環境:

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

--//如果不設定,也是預設設定.

$ 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

--//實際上這個時候是開啟自動調整.

--//如果你設定0,自動關閉這個功能.

2.設定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

--//提示一樣,但是現在是關閉的.

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

SID      NAME                   TYPE    VALUE

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

*        fast_start_mttr_target integer 0

--//你等很久觀察,這是WRITES_AUTOTUNE一直是0.

3.設定fast_start_mttr_target=200:

SYS@book> alter system set fast_start_mttr_target=200;

--//重新開機:

fast_start_mttr_target integer 200

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

*        fast_start_mttr_target integer 200

--//alert沒有mttr的相關顯示,表示已經MTTR advisory is enabled.