ORACLE初始化参数：STATISTICS_LEVEL的介绍

tiyna

初始化参数STATISTICS_LEVEL用于指定数据库和OS统计参数搜集级别，其取值为TYPICAL、BASIC和ALL，默认值为TYPICAL。

    当设置该参数为TYPICAL时，Oracle会搜集数据库自管理特征所需的主要统计；

    当设置该参数为BASIC时，oracle关闭了所有性能数据的收集,也就是如果要关闭AWR或statspack收集,只要设置alter system set statistics_level=basic;就行了;

    当设置该参数为ALL时，不仅会搜集TYPICAL的所有统计，还会搜集其他统计信息。

官网文档说明：

STATISTICS_LEVEL specifies the level of collection for database and operating system statistics. The Oracle Database collects these statistics for a variety of purposes, including making self-management decisions.

The default setting of TYPICAL ensures collection of all major statistics required for database self-management functionality and provides best overall performance. The default value should be adequate for most environments.

When the STATISTICS_LEVEL parameter is set to ALL, additional statistics are added to the set of statistics collected with the TYPICAL setting. The additional statistics are timed OS statistics and plan execution statistics.

Setting the STATISTICS_LEVEL parameter to BASIC disables the collection of many of the important statistics required by Oracle Database features and functionality, including:

• Automatic Workload Repository (AWR) Snapshots
• Automatic Database Diagnostic Monitor (ADDM)
• All server-generated alerts
• Automatic SGA Memory Management
• Automatic optimizer statistics collection
• Object level statistics
• End to End Application Tracing (V$CLIENT_STATS)
• Database time distribution statistics (V$SESS_TIME_MODEL and V$SYS_TIME_MODEL)
• Service level statistics
• Buffer cache advisory
• MTTR advisory
• Shared pool sizing advisory
• Segment level statistics
• PGA Target advisory
• Timed statistics
• Monitoring of statistics
  
  

Note:Oracle strongly recommends that you do not disable these important features and functionality.

When the STATISTICS_LEVEL parameter is modified by ALTER SYSTEM, all advisories or statistics are dynamically turned on or off, depending on the new value of STATISTICS_LEVEL. When modified by ALTER SESSION, the following advisories or statistics are turned on or off in the local session only. Their system-wide state is not changed:

• Timed statistics
• Timed OS statistics
• Plan execution statistics
  
  

The V$STATISTICS_LEVEL view displays information about the status of the statistics or advisories controlled by the STATISTICS_LEVEL parameter.

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