How to Check/Verify the ADDM is enabled in Oracle Database?

The Automatic Database Diagnostic Monitoring is enabled by default in Oracle database and it is determined by the initialization parameter called STATISTICS_LEVEL. There are 3 values allowed for this parameter – BASIC, ALL and TYPICAL. If the value for the parameter is set as TYPICAL or ALL then the ADDM is enabled for your database. If you set the value to BASIC many of the oracle features will get disabled including ADDM and it is strongly discouraged.