Download 1. Introduction to SQL Tuning

Introduction to SQL Tuning
Page 1
1. Introduction to
SQL Tuning
© 2001 SkillBuilders, Inc.
© 2001 SkillBuilders, Inc.
SKILLBUILDERS
V 1.3
Introduction to SQL Tuning
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Introduction to SQL Tuning
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Objectives
Ø Understand what can be tuned
Ø Understand what we need to know in order to
tune SQL
© 2001 SkillBuilders, Inc.
© 2001 SkillBuilders, Inc.
V 1.3
Introduction to SQL Tuning
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Introduction to SQL Tuning
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What Can Be Tuned?
Ø Data Access
Ø
Ø
SQL
Application Logic: 3GL code, PL/SQL
Ø Database server
Ø
Instance Tuning, Memory Tuning
Ø Utilities
Ø
SQL*Loader, Import/Export
Ø Network
Ø
Net8, network infrastructure
© 2001 SkillBuilders, Inc.
SQL statements such as SELECT, UPDATE and DELETE utilize the Oracle optimizer
to determine the fastest access path. However, we can influence the decision of the
optimizer when needed to alter the access path. This is the process of tuning the
statement.
Application logic can be tuned. For example, a 3GL such as C or COBOL can
incorporate array processing. PL/SQL can use bulk bind, available in Oracle8i.
The database server itself can be tuned - the sized of memory areas such as the database
buffer cache have a huge impact on overall performance. Also, tuning the background
processes such as DBWR and LGWR is possible.
Utilities such as SQL*LOADER can be tuned to optimize the loading of large amounts
of data in the the database. For example, the direct path optio n can significantly reduce
overall load times.
Finally, the network can be tuned. From and Oracle perspective, this would include
tuning Net8 (formerly SQL*Net). Options such as connection pooling can be critical
in today’s world of high access internet applications
© 2001 SkillBuilders, Inc.
V 1.3
Introduction to SQL Tuning
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Introduction to SQL Tuning
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What This Course Covers
Ø Data Access Tuning
Ø Tuning SQL Statements
Ø Tuning PL/SQL programs
© 2001 SkillBuilders, Inc.
In this course we will cover SQL tuning and application logic tuning, including tuning
PL/SQL programs.
Tuning the database server, network and utilities is covered in a database performance
tuning for administrators class.
© 2001 SkillBuilders, Inc.
V 1.3
Introduction to SQL Tuning
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Introduction to SQL Tuning
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Tuning SQL: What We
Need to Know
Ø Understand database processes
Ø
SQL statement execution, optimization, parallel
execution
Ø Understand database memory structures
Ø
Shared Pool, Database Buffer Cache
Ø Understand database objects
Ø
Ø
tables, indexes
B-Tree, Bitmap, Index-Organized Tables,
Based Indexes, Reverse Key Indexes
Function-
© 2001 SkillBuilders, Inc.
Tuning an SQL statement requires the understanding of many things about the database
such as:
Ø Database Processes - You must understand how a statement is executed by Oracle
and how the Oracle optimizer works. Also, parallelization is critical, especially in
multi-CPU environments.
Ø Memory Processes - You must understand the purpose of the shared pool and
database buffer cache.
Ø Database Objects - It is not possible to tune an SQL statement without
understanding indexes! Data storage in tables or clusters can also have an effect.
Ø Access Paths - The Oracle optimizer can choose from many different access paths.
You must understand what these are and which may provide better performance
under the current circumstances.
Ø Explain and Trace - You will need to learn the mechanics of determining what
is going on when you execute the statement you are trying to tune. Tools such as
EXPLAIN and trace allow us to see under the covers!
© 2001 SkillBuilders, Inc.
V 1.3
Introduction to SQL Tuning
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Tuning SQL: What We Need
to Know
Ø Understand Access Paths
Ø
Full Scans, Index Scans
Ø Learn to Explain and Trace Statements
Ø
Externalize access path being used - EXPLAIN
Ø Tune the SQL Statement!
Ø
Add, modify or drop indexes
Ø
use hints
Ø
recode the SQL statement
Ø
and more!
© 2001 SkillBuilders, Inc.
© 2001 SkillBuilders, Inc.
V 1.3
Introduction to SQL Tuning
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Introduction to SQL Tuning
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Tuning Programs: What We Need
to Know
Ø PL/SQL
Ø
Promote use of stored database objects
Ø
Packages
Ø
Bulk Binds
Ø General
Ø
Sequences
Ø
Ø
Deadlock avoidance
Rollback Segments
© 2001 SkillBuilders, Inc.
PL/SQL programs can be tuned. Just the proper use of stored PL/SQL programs will
increase the performance of your application, implementing PL/SQL packages and
techniques such as bulk bind will also increase performance.
Application performance (3GL or PL/SQL) can sometimes be improved with the use of
sequences, coding for deadlock avoidance and be segregating UNDO into a separate
rollback segment.
All of the techniques mentioned above will be covered in this course
© 2001 SkillBuilders, Inc.
V 1.3