The presentation will give tips for oracle database SQL tuning.

1. Oracle Performance Tuning
Presented By :
G.A.Dilruk

2. Agenda
 Oracle Tuning Overview
 Two Types of Oracle Tuning
 SQL Tuning Overview
 SQL Tuning Steps
 Writing Better SQL Statements
 Using Indexes

3. Oracle Tuning Overview
 Effective data collection and analysis is
essential for identifying and correcting
performance problems.
 Low hardware will affect response time but
wise versa is not true always.
 Increasing number of session pool will
increase performance too.

4. Two Types of Oracle Tuning
 Instance Tuning
 SQL Tuning

5. SQL Tuning Overview
 The goals of SQL tuning involve verifying
the best execution plan for any statements.
 Oracle support both automatic and manual
tuning.
 Considering End User Response Time and
Server Resource Usage.

6. SQL Tuning Overview
 If you INSERT into a table with three indexes, then it will be
approximately 10 times slower than an INSERT into a table
with no indexes.
 The worst type of view use is when a view references other
views, and when they are joined in queries.
 If you want SQL to accomplish different things, then write
various statements.
 Rewriting an inefficient SQL statement is easier than
modifying it.
 Using triggers consumes system resources. If you use too
many triggers, then you can find that performance is
adversely affected.

7. SQL Tuning Steps
 Identifying high load or low performing SQL
statements (Ref Ex01).
 Looking and Verifying oracle execution plan
(Ref Ex02).
 Implementing corrective action.
 Repeating above steps.

8. How Oracle Plan SQL
Execution
 Gather data statistics (oracle support both
automatic and manual data gathering) (Ref
Ex03).
 Query optimizer looking collected data and
plan better execution.

9. Writing Better SQL Statements
 Get only required columns in the select statement.
 Use untransformed column values in WHERE clauses
as much as possible.
 Beware of implicit type conversions.
 Combine Multiples Scans with CASE Statements.
 Use DML with RETURNING Clause.
 Modify All the Data Needed in Single SQL Statement.

10. Writing Better SQL Statements
Using Indexes
 Do not build indexes unless necessary.
 Consider indexing keys that are used frequently in WHERE
clauses.
 Consider indexing keys that are used frequently to join tables
in SQL statements.
 Columns that are frequently update are bad for indexing.
 Columns that have long character strings are bad for
indexing.
 Do not index keys that appear only in WHERE clauses with
functions or operators.

11. Writing Better SQL Statements
Index Types
 Oracle includes numerous data structures to improve
the speed of Oracle SQL queries.
 B-Tree Indexes are the most popular common index
type.
 Create composite indexes with correct column ordering.
 Use Bitmap Indexes for Performance.
 Use function-based index either in transformed columns
or in an expression.

12. Q & A

13. Thanks