The key features to the Diagnostic Pack for the database include
More information on all of these topics can be found in a variety of locations. Most of the information in this blog can be found at
ASH statistics are enhanced to provide row-level activity information for each captured SQL statement. This information can be used to identify which part of the SQL execution contributed most significantly to the SQL elapsed time. The ASH views, accessible to DBAs, provide historical information about the active sessions in the database.
The Automated Workload Repository (AWR) reports provide baseline statistics for the database and show the database performance during specified intervals. A baseline contains performance data from a specific time period that is preserved for comparison with other similar workload periods when performance problems occur. Several types of baselines are available in Oracle Database: fixed baselines, moving window baselines, and baseline templates.
DBAs and developers can use ADDM to analyze the database and generate recommendations for performance tuning. In Oracle 11g, ADDM was enhanced to perform analysis on database clusters on various levels of granularity (such as database cluster, database instance, or specific targets) over any specified time period.
You can access ADDM through SQL Developer or Enterprise Manager. To access these functions you must first enable the Diagnostics Pack which allows you access to the reports.
You can manually run the ADDM report with a command line
If we click on one of the finding with a Yes in the recommendation column we can look at the report and recommendations that it has. For the example we found it had two suggestions for tuning. Below are samples of this report and the two recommendations.
We can look at similar information from Enterprise Manager by navigating to the Performance page and selecting the report that we want.
Typical AWR report output usually contains an incredible amount of information about an Oracle database’s application workload behavior. When a database instance is suffering from a gc buffer busy wait event during the time period chosen for the AWR report, however, that event will usually surface as one of the Top 5 Timed Events
With AWR you can create a baseline and look at spot performance or variation from a baseline. Page 21 of Diagnostic Pack Presentation does a good job of describing how to read and understand an AWR Report. The blog Bash DBA does a good job of walking through an AWR and looking for issues and problems in a system.
In summary, we are not going to dive deep into AWR and ADDM diagnostics. Knowing how to do this differentiates a high paid DBA from a junior DBA. There are classes through Oracle Education - 12c Performance Management and Tuning and other vendors that teach you how to understand this option as well as the books we mentioned above and certification exams to help show that you know this material. It is important to note that all of these tools work with platform as a service (Oracle and Amazon RDS) as well as infrastructure as a service and on-premise installations. The key difference is that the diagnostic and tuning tools are bundled with the High Performance and Extreme Performance Editions. For IaaS and on-premise you need to purchase a perpetual license that we discussed a few blogs ago.