Difference between AWR, ADDM and ASH reports

AWR:

Automatic Workload Repository gathers, processes and maintains performance stats used for problem detection and self-tuning the databases.

Different Components that uses AWR are:

Automatic Database Diagnostic Monitor

Undo Advisor

SQL Tuning Advisor

Segment Advisor

Different types of AWR Reports for different purposes:

For Single Instance Environment:

@$ORACLE_HOME/rdbms/admin/awrrpt.sql

For Oracle RAC Environment :

@$ORACLE_HOME/rdbms/admin/awrgrpt.sql

For a particular SQL Statement :

@$ORACLE_HOME/rdbms/admin/awrsqrpt.sql

For Comparing the reports :

@$ORACLE_HOME/rdbms/admin/awrddrpt.sql

ADDM:

Automatic Database Diagnostic Monitoring Report analyzes the AWR data on a regular basis, to give you overview of the root cause of the problem which is affecting your database’s performance. It also provides suggestions or recommendations for rectifying any problem identified and lists the areas which are having no issues. ADDM recommends multiple solutions for the DBA to choose from which includes,

Database Configuration

Hardware changes

Schema changes

Application changes &

Other advisories

generate ADDM:

@$ORACLE_HOME/rdbms/admin/addmrpt.sql

ASH:

ASH is an integral part of the Oracle Database self-management framework and is extremely useful for diagnosing performance problems. ASH gathers sampled data at the session level rather than at the instance level. By capturing statistics for only active sessions, ASH collects a manageable set of data.

Below mentioned is the script which you can run to generate your ASH report,

@$ORACLE_HOME/rdbms/admin/ashrpt.sql

For Oracle RAC Environment :

@$ORACLE_HOME/rdbms/admin/ashrpti.sql