Use of the SQL Tuning Advisor
Use the SQL Tuning Advisor for tuning SQL statements. Typically, you can run this advisor in response to an ADDM performance finding that recommends its use.
Additionally, you can run the SQL Tuning Advisor on the most resource-intensive SQL statements, referred to as top SQL, from the cursor cache or the AWR, as well as on a user-defined SQL workload.
To run the SQL Tuning Advisor do the following:
- On the Home Page, under Related Links, click Advisor Central, then click SQL Tuning Advisor. The SQL Tuning Advisor Links page appears.
- The advisor can be run on one of the following sources:
Top SQL—These consist of recently active top SQL statements from the cursor cache (Spot SQL) or historical top SQL from the AWR (Period SQL).
SQL Tuning Sets—These consist of SQL statements you provide. An STS can be created from SQL statements captured by AWR snapshots or from any SQL workload.
- For example, you can select Top SQL. The Top SQL page appears. This page has two tabs, Spot SQL and Period SQL. Spot lists recent top SQL from the cursor cache, while Period SQL lists historical top SQL captured in the AWR. You must select an interval to analyze by dragging the shaded box over the period. You then select one or more SQL statements to analyze during the selected period.
- Click Run SQL Tuning Advisor. The SQL Tuning Options page appears showing the SQL statements in the interval. Give your task a name and description, select the scope for the analysis (Comprehensive or Limited), and select a start time for the task. Click OK.
- Navigate back to the Advisor Central page. The status of Advisor Tasks is listed under this heading in the results section. You must wait until your task status is
COMPLETED. You can check the status by clicking your browser's Refresh button. Then, select your task and click View Result.
- The SQL Tuning Result page appears. To view recommendations, select the SQL statement and click View Recommendations. The recommendation can include one or more of the following:
Create an index to offer alternate, faster access paths to the query optimizer.
Accept SQL profile, which contains additional SQL statistics specific to the statement that enables the query optimizer to generate a significantly better execution plan.
Gather optimizer statistics on objects with stale or no statistics.
Advice on how to rewrite a query for better performance.