STATISTICS_LEVEL

STATISTICS_LEVEL

Property	Description
Parameter type	String
Syntax	STATISTICS_LEVEL = { ALL | TYPICAL | BASIC }
Default value	TYPICAL
Modifiable	ALTER SESSION, ALTER SYSTEM

STATISTICS_LEVEL 指数据库与操作系统统计信息的收集级别，有三个可选的值: ALL | TYPICAL | BASIC，默认值为TYPICAL.Oracle推荐使用这些AWR，ADDM等这些重要的特性与功能，即不推荐将收集级别设置为BASIC.ALL级别会收集额外的OS统计信息与计划执行的统计信息（如：v$sql_plan_statistics）。

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

from oracle references