Level of Statistics Collection

Level of Statistics Collection
The level of statistic collection on the database is determined by the value of the
STATISTICS_LEVEL parameter. The values for this parameter are:
• Basic: No advisory or other statistical data is collected. You can manually set other
statistic collection parameters such as TIMED_STATISTICS and
DB_CACHE_ADVICE.
• Typical: This is the default value. Data is collected for segment level statistics, timed
statistics and all advisories. The value of other statistic collection parameters is
overridden.
• All: Collection is made of all the Typical level data, the timed operating system
statistics and the row source execution statistics. The value of other statistic
collection parameters is overridden.
Query v$statistics_level to determine which parameters are affected by the
STATISTICAL_LEVEL parameter.

These statistic parameters can also be set individually. These parameters are:
• TIMED_STATISTICS: Set to True to collect time statistics
• DB_CACHE_ADVICE: This parameter accepts the following values:
- Off
No statistics collected and no memory used.
- Ready
No statistics collected, but memory is allocated. Having DB_CACHE_ADVICE
set to Ready prevents memory errors when needing to collect statistics on
buffer cache utilization.
- On
Statistics collected and memory allocated. Changing the status of
DB_CACHE_ADVICE from Off to On can raise an error if the required memory
is not available.
• TIMED_OS_STATISTICS: Specifies the interval (in seconds) at which Oracle
collects operating system statistics when a request is made from the client to the
server or when a request completes.