STATISTICS_LEVEL

STATISTICS_LEVEL是控制DB_CACHE_ADVICE, TIMED_STATISTICS, or TIMED_OS_STATISTICS的主要参数。
If STATISTICS_LEVEL=TYPICAL or ALL时,不需要设置TIMED_STATISTICS;
If STATISTICS_LEVEL=BASIC时, 设置了TIMED_STATISTICS=TRUE才能统计时间信息。

当明确设定了DB_CACHE_ADVICE, TIMED_STATISTICS, or TIMED_OS_STATISTICS这几个参数的值后,系统会将由STATISTICS_LEVEL所设定的默认这些参数的值覆盖。

Metalink resource:
– STATISTICS_LEVEL

STATISTICS_LEVEL sets the statistics collection level of the database.

oracle9i Release 2 introduces a comprehensive set of advisories including shared
pool sizing advisor, SQL Execution Memory (PGA) Memory Advisor and Recovery Cost
Estimator. All the advisories in oracle9i Release 2 including the Buffer Cache
Advisor are controlled by a newly introduced parameter STATISTICS_LEVEL. The
Parameter DB_CACHE_ADVICE has, therefore, been deprecated in oracle9i Release 2.
By default, the STATISTICS_LEVEL parameter is set to TYPICAL thereby enabling
all the advisories. V$STATISTICS_LEVEL lists the status of the statistics or
advisories controlled by the STATISTICS_LEVEL initialization parameter. Each row
of V$STATISTICS_LEVEL represents one of these statistics or advisories. For more
details on the STATISTICS_LEVEL parameter, please refer to oracle9i Release 2
Performance Tuning Guide and Reference.

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