The STATISTICS_LEVEL initialization parameter controls the capture of a
variety of statistics and various advisors, including the automatic maintenance
tasks. The automatic maintenance tasks include gathering optimizer statistics.
The STATISTICS_LEVEL parameter can be set to the following levels:
BASIC: The computation of AWR statistics
and metrics is turned off. The automatic optimizer statistics task is disabled,
as are all advisors and server-generated alerts.
TYPICAL: Major statistics are collected
that are required for database self-management. They represent what is
typically needed to monitor Oracle database behavior. This includes automatic
gathering of statistics to reduce the likelihood of poorly performing SQL
statements due to stale or invalid statistics.
ALL: All possible statistics are
captured. This level of capture adds timed OS statistics and plan execution
statistics. These statistics are not needed in most cases and should not be
enabled for best performance; they are sometimes needed for specific
diagnostics tests.
Oracle recommends that the default value of TYPICAL be set for the STATISTICS_LEVEL
initialization parameter. Setting the value to BASIC disables the automatic
gathering of optimizer statistics.
