SQL plan management uses a mechanism called a SQL plan baseline. A plan baseline is a set of accepted plans that the optimizer is allowed to use for a SQL statement. In the typical use case, the database accepts a plan into the plan baseline only after verifying that the plan performs well.
What is difference between SQL profile and SQL baseline?
Think of it this way: SQL profiles give information to the optimizer to help select the best plan but don’t force the optimizer to select any specific plan. SQL plan baselines limit the optimizer plan selection to a set of accepted plans. … Use baselines when you want to use one of a specific set of plans.
What is SQL plan base line and have you created any time?
SQL Plan Baselines are a new feature in Oracle 11g that helps to prevent repeatedly used SQL statements from regressing because a newly generated execution plan is less effective than what was originally in the library cache.
What is baseline in database?
Baseline Data. The collection of all Information on the assets in the base year, which is used to establish the plan and track variances over the study period. See also: Database. Initial Study.
What is a baseline query?
Defined, a SQL Plan Baseline is a set of one or more “accepted” plans that contain hints, the plan hash value and other plan related data. In addition to the actual baseline, Oracle also maintains a SQL Plan History. … A statement has had three different execution plans generated.
How do I check if a SQL baseline is used?
Here’s the basic idea:
- run a statement that uses an index and check the plan.
- create a Baseline on the statement using the index (using my create_baseline. …
- check the hints stored with the baseline (using my baselines_hints. …
- run the statement again and check the real plan to see that the Baseline was used.
How do I create a baseline in SQL?
You can create a SQL plan baseline in several ways: using a SQL Tuning Set (STS); from the cursor cache; exporting from one database and importing into another; and automatically for every statement.
How do I use SQL Management plan?
Query the table using an unindexed column, which results in a full table scan. Identify the SQL_ID of the SQL statement by querying the V$SQL view. Use this SQL_ID to manually load the SQL plan baseline. The DBA_SQL_PLAN_BASELINES view provides information about the SQL plan baselines.
How do you force a hash value plan?
How to force SQL ID to use a specific hash
- Shows current plan. …
- Load SQL ID from cursor cache. …
- Load SQL ID from AWR. …
- Verify the execution Plan of a SQL_ID in the STS. …
- Load all plans from SQL Tuning Set. …
- Force a SQL statement to use specific hash. …
- Shows execution plan of sql plan. …
- Show all sql baselines.
How can I change SQL plan in Oracle?
Perform the following steps:
- Open Enterprise Manager DB Control and login as the system user.
- Select the Server tab.
- Under Query Optimizer, select SQL Plan Control.
- Select the SQL Plan Baseline tab.
- Under Settings, select the link FALSE for Capture SQL Plan Baselines.
How do I accept a baseline in SQL?
1 Answer. To enable baseline usage, optimizer_use_sql_plan_baselines must be true. Consider a baseline for the plan with the lowest cost or best elapsed time. The optimizer will choose the lowest cost accepted plan but will give preference to a fixed plan.
What is SQL plan management?
SQL plan management is a preventative mechanism that enables the optimizer to automatically manage execution plans, ensuring that the database uses only known or verified plans. Purpose of SQL Plan Management: The primary goal of SQL plan management is to prevent performance regressions caused by plan changes.
How do I pin a plan in Oracle?
Pin and unpin the Queries with DBMS SHARED POOL Package
- Run the Statement which you want to pin. SQL> SELECT ‘Example TEST’ FROM dual; …
- Check the Query in V$SQL. select substr(sql_text,1,15) Text,address,hash_value,KEPT_VERSIONS. …
- Pin the upper SQL with ADDRESS and HASH_VALUE parameter: …
- Check the Status of KEPT_VERSIONS.
Why SQL plan baseline is not used?
But optimizer just used to ignore existing SPB and switched to cost-based decision in order to produce an execution plan for a SQL statement. … Also, it is seen that dba_sql_plan_baselines. reproduced column was set to NO for this SPB.
What is a Hash plan?
sql oracle sql-execution-plan. When we execute any sql statement in Oracle, a hash value is being assigned to that sql statement and stored into the library cache. So, that later, if another user request the same query, then Oracle find the hash value and execute the same execution plan.
What is SQL tuning set in Oracle 12c?
A SQL tuning set (STS) is a database object that you can use as input to tuning tools. An STS includes: A set of SQL statements. Associated execution context, such as user schema, application module name and action, list of bind values, and the environment for SQL compilation of the cursor.