What is the Explain plan in Oracle?

What is the Explain plan in Oracle?

The EXPLAIN PLAN statement displays execution plans chosen by the Oracle optimizer for SELECT , UPDATE , INSERT , and DELETE statements. A statement’s execution plan is the sequence of operations Oracle performs to run the statement.

What is the difference between explain plan and execution plan in Oracle?

An explain plan predicts how Oracle will process your query. An execution plan describes the steps it actually took.

What is cost in Explain plan in Oracle?

Cost is the estimated amount of work the plan will do. A higher cardinality => you’re going to fetch more rows => you’re going to do more work => the query will take longer. Thus the cost is (usually) higher. All other things being equal, a query with a higher cost will use more resources and thus take longer to run.

What is plan hash value in Oracle?

This is the hash of the text of the SQL statement and is what Oracle uses to determine whether a particular SQL statement already exists in the shared pool. What you are showing in your example, however, is the plan_hash_value which is the hash of the plan that is generated for the SQL statement.

How do you use explain plan?

To explain a SQL statement, use the EXPLAIN PLAN FOR clause immediately before the statement. For example: EXPLAIN PLAN FOR SELECT last_name FROM employees; This explains the plan into the PLAN_TABLE table.

Where is explain plan stored in Oracle?

The explain plan process stores data in the PLAN_TABLE . This table can be located in the current schema or a shared schema and is created using in SQL*Plus as follows.

What is difference between execution and explain plan?

The explain plan is what the optimizer thinks will happen when you run, the execution plan is actually happened when you ran the query.

Where is explain plan in SQL Developer?

In SQL Developer, you don’t have to use EXPLAIN PLAN FOR statement. Press F10 or click the Explain Plan icon. It will be then displayed in the Explain Plan window.

How do you write an explain plan?

How to generate explain plan in oracle

1. Explain plan for a sql_id from cursor. set lines 2000 set pagesize 2000 SELECT * FROM table(DBMS_XPLAN.
2. Explain plan of a sql_id from AWR: SELECT * FROM table(DBMS_XPLAN.
3. Explain plan of sql baseline:
4. Explain plan for sql id from sql tuning set:

What is the plan hash value?

The plan hash value is merely an indicator of similar operations on database objects: filter and access predicates, which we shall discuss in more detail, are not part of the plan hash value calculation. For hard parses, the next station on the SQL compiler line is the query optimizer.

How do I know if execution plan has changed?

You can check if the SQL execution plan has changed by using the Active Workload Repository (AWR). First, you need to find the SQL_ID for the relevant query. The view GV$SQL contains the most recent SQL. If you can’t find the query in this view, try DBA_HIST_SQLTEXT instead.

What is an explain plan in SQL?

The EXPLAIN PLAN statement displays execution plans chosen by the optimizer for SELECT , UPDATE , INSERT , and DELETE statements. A statement execution plan is the sequence of operations that the database performs to run the statement.