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.
What is SQL plan?
A query plan (or query execution plan) is a sequence of steps used to access data in a SQL relational database management system. … When a query is submitted to the database, the query optimizer evaluates some of the different, correct possible plans for executing the query and returns what it considers the best option.
How do I check if a SQL baseline is used?
Displaying SQL Baseline Plans
- 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.
What are the different ways in which PL SQL can run?
You can run a procedure or function interactively by: Using an Oracle tool, such as SQL*Plus. Calling it explicitly in the code of a database application, such as an Oracle Forms or precompiler application. Calling it explicitly in the code of another procedure or trigger.
How do I accept a baseline in SQL?
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 difference between SQL profile and baseline?
When used together with its regular inputs, a SQL profile helps the optimizer minimize mistakes and thus more likely to select the best plan. A SQL plan baseline for a SQL statement consists of a set of accepted plans. When the statement is parsed, the optimizer will only select the best plan from among this set.
How can I tell if a SQL profile is used?
SQL Profile is used by Optimizer for use more efficient execution plan for the SQL Query to make in accepted State. It is found in DBA_SQL_PROFILES view. It used to choose better plan by optimizer if the SQL profile plan is having low cost then optimizer use it. Check the SQL Profile in the Database.
What is cost of a query?
Query cost is what optimizer thinks of how long your query will take (relative to total batch time). The optimizer tries to choose the optimal query plan by looking at your query and statistics of your data, trying several execution plans and selecting the least costly of them.
Where SQL plan is stored?
The SQL plan baselines are stored in a plan history in the SQL Management Base in the SYSAUX tablespace.
How do I force a plan in Oracle?
Answer: Oracle provides many ways to force an execution plan:
- Stored Outlines: Stored outlines will same an existing execution plan and force it to be used. …
- SQL Hints: Oracle hints are optimizer directives that can be used to force Oracle to always use the same execution plan for a SQL statement.
How do you get the explain plan for a query in Oracle?
Running EXPLAIN PLAN
EXPLAIN PLAN FOR SELECT last_name FROM employees; This explains the plan into the PLAN_TABLE table. You can then select the execution plan from PLAN_TABLE . This is useful if you do not have any other plans in PLAN_TABLE , or if you only want to look at the last statement.
What is a SQL profile?
A SQL profile is a set of auxiliary information specific to a SQL statement. Conceptually, a SQL profile is to a SQL statement what statistics are to a table or index. The database can use the auxiliary information to improve execution plans. … Therefore, SQL profiles just guide the optimizer to a better plan.