How do you use Oracle’s SQL Plan Management (SPM) feature to manage and control execution plans for optimal performance?

Oracle’s SQL Plan Management (SPM) feature is designed to manage and control execution plans for optimal performance in Oracle databases. It enables the database to automatically capture and evaluate execution plans for SQL statements, and choose the best plan for execution.

SPM can be used to control and manage execution plans by performing the following tasks:

1. Automatic plan capture: SPM automatically captures execution plans for all SQL statements that are executed as part of the workload.

2. Plan selection: SPM selects the best execution plan for each SQL statement based on the performance of the plans in the SQL plan baseline.

3. Plan evolution: SPM can automatically evolve execution plans over time by comparing new plans to existing ones in the SQL plan baseline, and accepting new plans that are better than the existing ones.

4. Plan verification: SPM can verify the performance of new execution plans before accepting them into the SQL plan baseline.

5. Plan removal: SPM can remove poorly performing execution plans from the SQL plan baseline to ensure that they are not selected for execution in the future.

To use SPM, the following steps are recommended:

1. Enable Automatic Plan Capture: Firstly, you need to enable automatic plan capture by setting the initialization parameter optimizer_capture_sql_plan_baselines to true.

2. Create a SQL Plan Baseline: You then need to create an SQL plan baseline using the DBMS_SPM.CREATE_SQL_PLAN_BASELINE procedure. This baseline specifies which execution plans are acceptable for a particular SQL statement.

3. Load the plan capture information: Once the SQL plan baseline is created, you can load the plan capture information by running the
DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE or
DBMS_SPM.LOAD_PLANS_FROM_SQLSET procedure.

4. Evolve plans: You can then introduce new execution plans into the SQL plan baseline by running the DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE procedure. This procedure compares new plans to existing ones and accepts the better plan.

5. Perform analysis of SPM performance: You are would need to monitor the performance of SPM over time to ensure that it is working correctly. You can do this by querying the V$SQL_PLAN view to see the execution plans for each SQL statement, and the DBA_SQL_PLAN_BASELINES view to see the execution plans that are part of the SQL plan baseline.

Below is an example of how to use SPM to manage execution plans:

-- Enable automatic plan capture
ALTER SYSTEM SET optimizer_capture_sql_plan_baselines=true;

-- Create an SQL plan baseline for a particular SQL statement
EXEC DBMS_SPM.CREATE_SQL_PLAN_BASELINE(sql_handle => 'INSERT INTO my_table VALUES (:B1, :B2)',
   plan_name => 'my_plan', owner => 'my_schema');

-- Load the plan capture information from the cursor cache for the SQL statement
EXEC DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE(sql_text => 'INSERT INTO my_table VALUES (:B1, :B2)');

-- Evolve the SQL plan baseline to introduce new execution plans
EXEC DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(sql_handle => 'INSERT INTO my_table VALUES (:B1, :B2)',
   plan_name => 'my_plan');

-- Analyze the performance of SPM by querying the V$SQL_PLAN and DBA_SQL_PLAN_BASELINES views
SELECT * FROM V$SQL_PLAN WHERE sql_id = 'sql_id';

SELECT * FROM DBA_SQL_PLAN_BASELINES WHERE sql_handle = 'sql_handle';

In conclusion, SPM is a powerful feature that can help manage and control execution plans for optimal performance. With proper setup and frequent analysis, it can greatly improve the performance of a database.