Oracle TIMED_STATISTICS 引數 說明

MOS上有關TIMED_STATISTICS引數說明：

Init.ora Parameter "TIMED_STATISTICS" Reference Note [ID 30824.1]

Health CheckAlert: Consider setting TIMED_STATISTICS and STATISTICS_LEVEL to recommendedlevels [ID 957433.1]

 

 

Version	Parameter		Type	Modifiable
11.1.0.7	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
11.1.0.6	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
10.2.0.4	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
10.2.0.3	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
10.1.0.5	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
10.1.0.4	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
9.2.0.8	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
9.0.1.4	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)
8.1.7.4	timed_statistics	BOOLEAN	ALTER SESSION ALTER SYSTEM (IMMEDIATE)

 

TIMED_STATISTICSspecifies whether or not statistics related to time are collected. It isimportant to set TIMED_STATISTICS=TRUE for obtaining timing information whichwill help in tuning the database.

--TIMED_STATISTICS 指定是否收集於時間相關的統計資訊，當設定為TURE時會獲取有關時間的更多資訊，從而幫助我們來優化DB.

 

有如下三種方法來設定該引數：

（1）初始化引數

The parameter can be set in theinitialisation file e.g.

timed_statistics= TRUE

 

（2）system 級別：

This parameter can be set at system levele.g.

ALTER SYSTEM SETtimed_statistics = TRUE

 

（3）session 級別：

This parameter can be set at session levele.g.

   ALTER SESSION SET timed_statistics = TRUE

 

 

When TIMED_STATISTICS is enabled statistics are generated for the following：

（1）PARSE, EXEC and FETCH CPU costs intrace files

（2）V$WAITSTAT

（3）V$FILESTAT and V$TEMPSTAT

（4）V$SYSSTAT and V$SESSTAT timedstatistics

 

Statistics affected by enabling TIMED_STATISTICS include

CPU used when call started CPU used by this session parse time cpu parse time elapsed redo write time session connect time

 

Wait times arerecorded in V$SESSION_EVENT, V$SYSTEM_EVENT and V$SESSION_WAIT irrespective ofthe setting of TIMED_STATISTICS (9.2.0)

 

關於該引數的預設值，在官網上有關TIMED_STATISTICS 引數的說明：

http://docs.oracle.com/cd/E11882_01/server.112/e25513/initparams255.htm#REFRN10218

 

If STATISTICS_LEVEL is set to TYPICAL or ALL,then true

If STATISTICS_LEVEL is set to BASIC,then false

 

如果STATISTICS_LEVEL 設定為TYPICAL或者ALL,那麼TIMED_STATISTICS 則預設為true。 如果STATISTICS_LEVEL設定為BASIC，則TIMED_STATISTICS 預設為false。

 

MOS上對STATISTICS_LEVEL的說明：

STATISTICS_LEVELspecifies the level of collection for the database and operating systemstatistics. The Oracle Database collects these statistics for a variety ofreasons, including making self-management decisions. Setting theSTATISTICS_LEVEL parameter to BASIC disables the collection of many importantstatistics required by Oracle Database features and functionality.STATISTICS_LEVEL=ALL should only be set for diagnostic purposes as required.

 

有關該引數在之前整理的Blog裡有說明：

Oracle Statistic 統計資訊 小結

http://blog.csdn.net/tianlesoftware/article/details/4668723

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