The Automatic Workload Repository (AWR) collects, processes, and maintains performance statistics for problem detection and self-tuning purposes.
This data is both in memory and stored in the database. The gathered data can be displayed in both reports and views.
The statistics collected and processed by AWR include:
Object statistics that determine both access and usage statistics of database segments.
Time model statistics based on time usage for activities, displayed in the V$SYS_TIME_MODEL and V$SESS_TIME_MODEL views.
Some of the system and session statistics collected in the V$SYSSTAT and V$SESSTAT views.
SQL statements that are producing the highest load on the system, based on criteria such as elapsed time and CPU time.
ASH statistics, representing the history of recent sessions activity.
Gathering database statistics using the AWR is enabled by default and is controlled by the STATISTICS_LEVEL initialization parameter.
The STATISTICS_LEVEL parameter should be set to the TYPICAL or ALL to enable statistics gathering by the AWR.
The default setting is TYPICAL. Setting STATISTICS_LEVEL to BASIC disables many Oracle Database features, including the AWR, and is not recommended.
If STATISTICS_LEVEL is set to BASIC, you can still manually capture AWR statistics using the DBMS_WORKLOAD_REPOSITORY package.
Jan 16, 2014
