Yuan Yao, An Oracle ACE's Blog

To use the Automatic Workload Repository (AWR), the STATISTICS_LEVEL parameter must be set to either TYPICAL or ALL. The default setting is TYPICAL.

SQL>  show parameter STATISTICS_LEVEL
NAME                    TYPE   VALUE
----------------------- ------ -------
client_statistics_level string TYPICAL
statistics_level        string TYPICAL

The parameter can be changed online. Setting STATISTICS_LEVEL to BASIC disables many Oracle Database features, including AWR, and is not recommended.

It’s important to note that using AWR requires a Diagnostic Pack license which incurs an additional cost. Without this license, accessing AWR views and reports is not legally permissible. You can manage the availability of packs to users by configuring the CONTROL_MANAGEMENT_PACK_ACCESS parameter appropriately.

SQL>  SHOW PARAMETER control_management_pack_access
NAME                           TYPE   VALUE
------------------------------ ------ -----------------
control_management_pack_access string DIAGNOSTIC+TUNING

By default, this parameter is set to DIAGNOSTIC+TUNING on Enterprise Edition , while on other editions, it is set to NONE.

SQL> alter system set control_management_pack_access=NONE;

System altered.

To use AWR, you need to set CONTROL_MANAGEMENT_PACK_ACCESS to either DIAGNOSTIC+TUNING or DIAGNOSTIC, this parameter can also be changed online. When this parameter is set to NONE, the AWR is disable. Although you can seemingly create snapshots and create AWR reports, these snapshots will contain no data, and the AWR reports will be almost empty.

Without the Diagnostic Pack license, you can still use Statspack, which is a legacy solution with reduced functionality. However, the knowledge required to interpret an AWR report is almost the same as that needed for Statspack.