This is a preview of the forthcoming book Oracle 11g New Features from Rampant TechPress, featuring John Garmany, Steve Karam and Lutz Hartmann.
Go back to "Inside the Oracle 11g SQL Performance Advisor, part 1."
The SPA treatment
The SQL Performance Analyzer (SPA) allows the DBA to define the SQL Tuning set (the STS) as a source for the test (usually using historical SQL from the AWR tables).
The SPA receives one or more SQL statements as input and provides advice on which tuning conditions have the best execution plans, gives the proof for the advice, shows an estimated performance benefit, and allegedly has a facility to automatically implement changes that are more than three times faster than the "before" condition.
Gathering the SQL Tuning set
The SQL workload (the STS) can be thought of as a container for conducting and analyzing many SQL statements. The STS is fed to the SPA for real-world execution with before-and-after comparisons of changes to holistic "environmental" conditions, specifically CBO levels or changed init.ora parameters.
Internally, the SPA is stored as a database object that contains one or more SQL statements combined with their execution statistics and context such as particular schema, application module name, list of bind variables, etc. The STS also includes a set of basic execution statistics such as CPU and elapsed times, disk reads and buffer gets, number of executions, etc.
When creating an STS, the SQL statements can be filtered by different patterns such as application module name or execution statistics such as high disk reads. Once created, STS can be an input source for the SQL Tuning Advisor.
Typically, the following steps are used to define the STS using the dbms_sqltune package. The steps within the new 11g OEM screen for "guided workflow" are simple and straightforward and serve as an online interface to the dbms_sqltune
To continue reading for free, register below or login
To read more you must become a member of SearchOracle.com
.create_sqlset procedure:
There is an interface to the SQL Performance Analyzer in the Enterprise Manager in the OEM Advisor Central area, and a number of new to dba_advisor views have been added in 11g which will display information from the SPA.
The technology behind SPA is encapsulated inside a new package called dbms_sqlpa. Here is an overview for the procedures of the dbms_sqlpa package:
In sum, the new 11g SQL Performance Analyzer is a great way to test for holistic tuning changes. Remember, the savvy Oracle DBA will always adjust their Oracle initialization parameters to optimize as much of the workload as possible before diving into the tuning of specific SQL statements.
Oracle 11g guided workflow screen
The OEM screen for the SPA guided workflow contains a predefined set of steps for holistic SQL workload tuning:
Using the guided workflow functionality, we can take our SQL tuning set and execute it twice (before and after), saving the SQL execution results (disk reads, buffer gets) using some of the common SQL execution metrics found in the dba_hist_sqlstat table:
Here it's important to note that the guided workflow does not measure these important SQL execution metrics such as sorts and fetches.
Comparing the SPA results
The final step in SPA allows the DBA to quickly isolate suboptimal SQL statements and tune them with the 11g SQLTuning Advisor. When viewing the results, you can use OEM for a visual display of all delta values between the execution run, but most important, you can do a side-by-side comparison of the before-and-after execution plans.
Oracle has always been ahead of the curve in automating well-structured DBA tasks, and the SPA is just the latest incarnation in real-world SQL tuning tools. Tools such as SPA free up the DBA to pursue other important DBA tasks, relieving them of the tedium of individually tuning SQL statements.
