Wiley Professional Oracle Programming Jun 2005-0764574825

Architecture and Performance Considerations 475Summary 485 Existing Java Class as a Persistent Object Type 501 Creating Instances of Object Types in the Database 504 Summary 520 Protocol

Professional Oracle® Programming Rick Greenwald, Robert Stackowiak, Gary Dodge, David Klein, Ben Shapiro,

Christopher G Chelliah

Professional Oracle® Programming

Professional Oracle® Programming Rick Greenwald, Robert Stackowiak, Gary Dodge, David Klein, Ben Shapiro,

Christopher G Chelliah

Copyright © 2005 by Wiley Publishing Inc All rights reserved.

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Published simultaneously in Canada

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Library of Congress Cataloging-in-Publication Data:

Professional Oracle programming / Rick Greenwald [et al.]

ISBN 10: 0-7645-7482-5

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

1B/QS/QW/QV/IN

About the Authors

Rick Greenwaldhas been in the technology industry for over 20 years and is the author of 12 previousbooks, most of them on Oracle He has been involved with development and databases for his entirecareer, including stops at Data General, Cognos, Gupta Technologies, and his current employer, Oracle.Computers and computing are a sideline for Rick — his real job is father to his three wonderful girls,with a primary hobby of music appreciation

Robert Stackowiakis Senior Director of Business Intelligence (BI) in Oracle’s Technology Business Unit

He is recognized worldwide for his expertise in business intelligence and data warehousing in leadingthe North American BI team at Oracle His background includes over 20 years in IT related roles atOracle, IBM, Harris Computer Systems, and the U.S Army Corps of Engineers including management

of technical teams, software development, sales and sales consulting, systems engineering, and businessdevelopment

Gary Dodge has been focused on database technology since his first COBOL programming job with IMSDB/DC in 1976 He joined Oracle Corporation in 1987 and has served in various management and technical positions within both the sales and consulting divisions He has been a frequent speaker ondatabase topics at many local and national information technology conferences In addition to several

magazine articles, he is co-author (with Tim Gorman) of Oracle8 Data Warehousing and Essential Oracle8i

Data Warehousing, both published by John Wiley & Sons

David Kleinhas been in the technology industry for over 20 years with a variety of companies, includingData General, Wang Laboratories, Gupta Technologies, Oracle, and a few consulting services companies

He has had many roles, including management of application development and database design teams,sales and sales consulting, systems engineering and marketing Recently, he has focused on developingclassroom and online training courses An active wife and two boys and a 200-year-old house take up anyfree time

Ben Shapirois the president of ObjectArts Inc., a New York City-based technology consulting company,and has been designing database systems with Oracle since 1997 ObjectArts has worked with manylarge corporate clients developing XML-based publishing tools and web-based applications BeforeObjectArts, Ben worked with several NYC-based startup companies as a technical lead building contentmanagement software

Christopher G Chelliahjoined Oracle as a Consultant in 1995 He brings with him project management,architecture, and development experience from a number of large, multinational sites in the mining, oiland gas, and telecom industries Chris has been involved with emerging and database technologies forhis entire career and is an accomplished software architect with a flair for business development Hisexpertise has been actively sought by a number of major Oracle clients in Australia, Europe, and theUnited States Chris, his wife and two kids are currently in Singapore, where he leads a team definingand executing on innovative E-Government strategies for Oracle’s Public Sector industry in Asia Pacific

Mary Beth Wakefield

Senior Production Editor

Text Design & Composition

Wiley Composition Services

of labor pains, the worth and beauty of this offspring owes an enormous amount to them.

Rick Greenwald, in particular, would like to thank two people First of all, the process of writing three (is it three already) titles and several revisions of books with Bob Stackowiak has been a wonderful experience, both professionally and personally I am delighted to count Bob as a friend, and, thanks tohim, I still don’t know what BI stands for

Secondly, throughout my writing career, Steven Feurstein has been a mentor as well as a sterling example

of what an author and person should be like I hope to someday reach his level in terms of writing and,even more importantly, humanity

And, of course, I would like to thank my family — LuAnn for helping me have a life that supports writingand working, and Elinor Vera, Josephine, and Robin Greenwald for giving me all the inspiration anyonewould ever need

In addition, Rick would like to acknowledge all those people who came through with suggestions andknowledge at crucial times, including Richard Foote, Raj Mattamal and Tyler Muth

Normalization 54

Denormalization 63

Chapter 6: The Oracle Data Dictionary 93

Summary 112

B-Tree Indexes 193

Oracle’s Built-In SQL Functions 268

Chapter 14: Distributed Queries, Transactions, and Databases 315

Working with Collections 366

Summary 396

xxi

Architecture and Performance Considerations 475

Summary 485

Existing Java Class as a Persistent Object Type 501 Creating Instances of Object Types in the Database 504

Summary 520

Protocol-Based Access to XML in the Oracle Repository 522 SQL-Based Access to XML Data in the Oracle Repository 529 Enabling a New Schema for Use with XDB Repositories 533

Creating the Content Management Application Front End 558

Summary 627

Summary 638

SQL*Loader 640

Transformations 643

Partitioning and the Speed of ETL 645

Summary 652

Summary 669

Windows Functions for Cumulative and Moving Aggregates 675

Summary 723

Introduction

Professional Oracle Programming is intended for application developers who use Oracle as their database.

As such, this book does not devote much space to topics which are primarily of interest to databaseadministrators, such as backup and recovery Most importantly, this book is designed to help a program-mer understand the database issues that can have a direct impact on the operation and performance oftheir applications

What Does This Book Cover?

Although it is impossible to cover all the topics that a professional developer could use to the level ofdepth required in a single book, this volume attempts to provide a foundation for these developers, aswell as guidance and examples of some of the key areas of interest and necessity These areas includeaccessing data using SQL, handling issues such as multi-user concurrency and data integrity and security,the basics of programming with Java, PL/SQL and XML, and data warehousing For a more completelist of topics, please refer to the section called “How Is This Book Structured?” later in this introduction

Who Is This Book For?

The entire topic of Oracle databases is certainly not a new one Oracle has been one of, if not the, leadingdatabases in the world for almost two decades now The standard Oracle documentation runs over 13,000pages, and leaves out a lot of the good stuff Determining the proper audience for this book, and writing

at a level appropriate for that audience, was the biggest conceptual challenge for all of the authors.Through discussions early in this project, the authors and publishers of this book came up with a fairlydistinct profile of our presumed reader This book is intended for people whose primary job is to createapplication systems They are developers, rather than database administrators

Following through on this profile, we believe that you, the professional developer, are well informedand skilled in the creation of these application systems In our experience, even professional developersmay think of the database they use as nothing more than a place to store data

This description of you, the target reader, has guided the selection of topics as well as the actual content

of this book

What You Need to Use This Book

Although you do not necessarily need to have a working instance of an Oracle database to benefit fromthis book, the book includes many examples that can be run against your Oracle database

All of the examples have been created against Oracle Database 10g, although, with a few noted exceptions,

you could run the examples against Oracle9i Since Oracle is a cross-platform database, the actual

operating system that your version of Oracle runs on is unimportant

All of the examples can be run in either the standard Oracle utilities, such as iSQL*Plus, that come withthe product, or a standard development environment, including tools such as TOAD Directions on how

to run the examples are included in Chapter 7 of this book on installing an Oracle database, or in thechapter in which the examples are given

Most of the screen shots in this book have used a Windows client platform, but that platform is simply astandard used for consistency, not a requirement

How Is This Book Str uctured?

In a broad sense, this book is divided up into three main areas — information you need to know abouthow the Oracle database works, information that can help you to use the capabilities of the Oracledatabase in creating your application systems, and information to help you achieve optimal performancewith your application systems Although these three areas are covered in the order listed in the book,you will find relevant information for each of these areas throughout all of the chapters, along with tips,techniques, and code samples

Part I: Oracle Essentials

Although the Oracle database is a standards-compliant SQL database, the architecture of the Oracledatabase and the way it operates include some unique features that are crucial to your effective use ofOracle The first part of Oracle for Professional Developers covers topics that every developer mustunderstand in order to use the Oracle database effectively Please don’t think of these chapters as simplyintroductory material, since some of the information in these chapters can have an enormous effect onthe eventual operation of your applications

The topics covered in this section include:

❑ A brief introduction to the architecture and components of the Oracle database

❑ A detailed look at how Oracle processes your SQL requests and the impact this can have onyour application code

❑ A description of how Oracle handles data access by multiple users, and how this impacts yourapplication design

❑ A primer on effective database design

❑ A discussion on how Oracle administers security and how you can use this for your applications

❑ An overview of the Oracle data dictionary, which contains information about the objects andoperations of a specific Oracle database

❑ A brief tutorial on installing an Oracle database

Part II: Data Topics

The second section of this book focuses on how to access and manipulate the data in the Oracledatabase The topics in this section are relevant to all developers, regardless of the language they areusing to implement their applications

The topics covered in this section include:

❑ An introdution to both basic SQL and some of the more sophisticated uses of this powerful dataaccess language

❑ Indexes, which help to speed the performance of data retrieval

❑ Constraints, which are used to both validate and limit the data added to your Oracle database

❑ A discussion of a variety of other database objects, such as sequences

❑ The use of functions, both built-ins that come with the Oracle database and your own customdefined functions

❑ A discussion of data manipulation as a distributed database environment

Part III: Database Programming Languages

The Oracle database allows you to include logic that runs in the database itself.Traditionally, the language

used for this work is PL/SQL — a set of procedural extensions based on the SQL language Oracle8i

introduced a Java engine into the database, which allowed you to use this language for implementingprocedural logic in the database

Part III of this book includes three chapters on PL/SQL and one on Java The PL/SQL chapters are dividedinto one on the basics of PL/SQL, one on using PL/SQL in conjunction with SQL, and one of PL/SQLpackages, which are a way of organizing and exposing the logic you create with PL/SQL

Part IV: Programming Techniques

Part IV of this book dives into the wide and varied area of implementing logic with various programmingtechniques to use in the database and your applications

The topics covered include:

❑ The use of triggers, which contain logic that is automatically executed whenever certain types ofdata access and manipulation are performed

❑ Regular expressions, which are a powerful syntax for implementing matching conditions, and

the expression filter — both of these features are new with Oracle Database 10g

❑ The use of your Oracle database with object types, both for storage and for interactions withobjects in your applications

❑ The use of Oracle with XML

❑ HTML-DB, a development environment that comes as part of Oracle Database 10g

Part V: Business Intelligence Techniques

Business intelligence describes the process of using raw data in a database as the raw material for analysisthat can affect the direction of business operations Business intelligence in the Oracle database encompassesthe use of several specific features and techniques, which are covered in this section

The topics covered include:

❑ Moving data between different databases, which is often used to take data from an OLTP system

to a system used for business intelligence

❑ Data loading and management, which covers the manipulations that are sometimes required toprepare data for use in business intelligence operations

❑ And specific query features used for business intelligence, such as analytic functions

Part VI: Optimization

Creating an application is the first part of any programming project But no application will be acceptable

to your constituents if it does not run efficiently

This final section of the book introduces you to the concepts behind optimization in the Oracle database.The chapter includes a discussion of how Oracle determines the optimal access paths to your data, how

to see what Oracle has determined, and how to shape the behavior of your Oracle database in this area.Although database optimization is a subject worthy of many excellent volumes, this chapter is intended

to give you all the information you need to start to make your applications perform well

The Bigger Picture

As mentioned at the start of this introduction, no one book is complete enough to cover everything youwill need to know to use Oracle as an effective database for your applications We have tried to give you

a map that can be used over the course of many years of working with an Oracle database If you believethat there are destinations we have left off of this map, or descriptions that could be more useful orinformative, we welcome your comments

Conventions

To help you get the most from the text and keep track of what’s happening, we’ve used a number of conventions throughout the book

Tips, hints, tricks, and asides to the current discussion are offset and placed in italics like this.

As for styles in the text:

❑ We highlight important words when we introduce them

❑ We show keyboard strokes like this: Ctrl+A

❑ We show file names, URLs, and code within the text like so: persistence.properties

❑ We present code in two different ways:

In code examples we highlight new and important code with a graybackground

The gray highlighting is not used for code that’s less important inthe present context, or has been shown before

Source Code

As you work through the examples in this book, you may choose either to type in all the code manually

or to use the source code files that accompany the book All of the source code used in this book is available for download at http://www.wrox.com Once at the site, simply locate the book’s title (either

by using the Search box or by using one of the title lists) and click the Download Code link on the book’sdetail page to obtain all the source code for the book

Because many books have similar titles, you may find it easiest to search by ISBN; for this book the ISBN is 0-7645-7482-5.

Once you download the code, just decompress it with your favorite compression tool Alternately, youcan go to the main Wrox code download page at http://www.wrox.com/dynamic/books/

download.aspxto see the code available for this book and all other Wrox books

Errata

We make every effort to ensure that there are no errors in the text or in the code However, no one is perfect, and mistakes do occur If you find an error in one of our books, like a spelling mistake or faultypiece of code, we would be very grateful for your feedback By sending in errata you may save anotherreader hours of frustration and at the same time you will be helping us provide even higher qualityinformation

Boxes like this one hold important, not-to-be forgotten information that is directly relevant to the surrounding text.

To find the errata page for this book, go to http://www.wrox.comand locate the title using the Searchbox or one of the title lists Then, on the book details page, click the Book Errata link On this page you canview all errata that has been submitted for this book and posted by Wrox editors A complete book listincluding links to each book’s errata is also available at www.wrox.com/misc-pages/booklist.shtml.

If you don’t spot “your” error on the Book Errata page, go to www.wrox.com/contact/techsupport.shtml

and complete the form there to send us the error you have found We’ll check the information and, if ate, post a message to the book’s errata page and fix the problem in subsequent editions of the book

appropri-p2p.wrox.com

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Oracle Architecture

and Storage

The core theoretical purpose of a relational database is to separate logical interaction with datawithin the database from the physical storage of that data As a user or developer, you shouldn’treally have to know how an Oracle database works internally, or stores its data, in order to use itproperly At a high level, this is certainly true You don’t need to know anything about the Oracledatabase to write SQL, the access language used to interact with the database, or to create programsthat use SQL

The Oracle database automatically takes care of translating your logical requests to access the datawithin its control But, like all applications, the way your Oracle database is actually implementedcan have an impact on what you do and do not do in the creation and maintenance of your applicationsystems Having a basic understanding of how Oracle does its jobs provides a foundation for the rest

of this book And understanding the ways that Oracle stores your data, which is also covered in thischapter, can have a direct impact on the way you write your applications that use that data

This first chapter introduces you to a lot of the behind-the-scenes underpinnings of the Oracledatabase — the architecture of the database and how the data is stored within it You very wellmay not ever have to use this information in your day-to-day tasks, but the substance of this chapter is necessary for the more detailed information about programming

This chapter covers the architecture of the Oracle database as well as the storage options for yourdata Depending on how the responsibilities are divided in your particular environment, there may

be database administrators (DBAs) who do most of the work of translating your logical requirementsinto physical storage, or you may be called upon to perform some of these tasks yourself In eithercase, this chapter gives you some familiarity with the way your Oracle database handles your data

The Oracle database is a relational database The theory of relational databases was first put forward by

Dr E F Codd, a research scientist working for IBM, in the mid-1970s Codd proposed a number of rulesfor a database to follow to be considered a relational database For the first decade or so after these ruleswere proposed, early relational databases fought to show that they were the most compliant with Codd’srules Those early days are far behind us now, and the basic features of a relational database, such as guar-anteeing transactional integrity and allowing ad hoc access to data, are well established in all major rela-tional databases

The Oracle database consists of two main parts: the instance, which is the software service that acts as anintermediary between application requests and its data, and the actual data files, which are where the data iskept The instance is a dynamic process and uses a variety of tasks and memory to support its operations Thedata files are stored on disk, so the data itself will survive most service interruptions, except for catastrophicmedia failure

The Instance

The Oracle instance is the collection of processes that handle requests from a client for a data Some ofthese processes are shown in Figure 1-1 Figure 1-1 also includes some of the main areas of memory that

an instance uses

Figure 1-1: Oracle instance architecture

An Oracle instance is either started as part of the process of booting a server or can be started explicitlywith commands Although you start an instance with a single command, there are actually three distinctsteps in the startup process:

❑ Starting the instance process itself

PGA

User User

User User

User

Redo Log buffers

❑ Mounting the database, which consists of opening the control files for the instance

❑ Opening the database, which makes the database available for user requests

An instance can be stopped with another command or via the system console, which follows the samesequence of events in reverse You can stop an instance gracefully by stopping users from logging on tothe database and only shutting down when the last active user has logged off, or you can simply stopthe instance, which may result in incomplete transactions (described in detail in Chapter 3, “HandlingMultiple Users”)

Processes Supporting an Instance

A number of processes are associated with an instance and perform specific tasks for the instance

Listener

The Listener is a process that listens on the network for requests coming in to an Oracle instance A Listenerprocess can support one or more Oracle instances The Listener acts as the intermediary between userrequests from remote machines and the instance The failure of the Listener will mean that the instance itsupports is not accessible by a remote client — such as any application that accesses the instance

Files Supporting an Instance

There are a number of files that are used by an instance The basic files for storing data are discussed in thenext section on data organization An Oracle instance has its own set of files that do not store user databut are used to monitor and manage the Oracle instance itself

Initialization Files

Many parameters exist that affect the way that your Oracle instance operates These parameters are typically set and maintained by a database administrator and, as such, are beyond the scope of this book.The initial values for these parameters are kept in initialization files

3

Prior to Oracle9i, each instance had its own specific initialization file called INIT.ORA, as well as an optional file with additional configuration information called CONFIG.ORA Starting with Oracle9i, you

could have a virtual initialization file called the SPFILE, which could be shared with multiple instances.SPFILE was especially handy for two reasons: You could change a configuration parameter for a runninginstance and not have to save the change to the SPFILE, which means that the value of the parameterwould be reset to the stored value on the next startup You can also use the SPFILE with Real ApplicationClusters, discussed later in this chapter, where multiple instances worked together in a cluster and sharedthe same initialization procedures

Control File

The control file is used to store key information about an instance, such as the name of the instance, thetime the database was created, and the state of backup and log files for the database An Oracle instancerequires a control file in order to operate Although a control can be rebuilt, most Oracle installations usemultiple copies of the control file to avoid this possibility

Redo Log Files

One of key features of a relational database is its ability to recover to a logically consistent state, even inthe event of a failure Every relational database, including Oracle, uses a set of redo log files These fileskeep track of every interaction with the database In the event of a database failure, an administrator canrecover the database by restoring the last backup and then applying the redo log files to replay userinteractions with the database

Redo log files eventually fill up and roll over to start a new volume You can set up Oracle to avoid writingover existing logfiles by creating the database to automatically archive log files in ARCHIVELOG mode,which is discussed in detail in the Oracle documentation

Since redo logs are crucial for restoring a database in the event of a failure, many Oracle shops set up aninstance to keep multiple copies of a redo log file

Rollback Segments

Unlike all other major databases, Oracle also uses rollback segments to store previous versions of data inthe database The use of rollback segments makes it possible for the Oracle database to avoid the use ofread locks, which can significantly reduce performance degradation based on multiuser access as well asproviding a consistent view of data at any particular point in time For more on rollback segments andhow they support multiuser concurrency, see Chapter 3, “Handling Multiple Users,” which covers thisimportant topic in detail

Because rollback segments track every change to data, the rollback segments are updated as soon as achange is made This real-time update lets the Oracle database delay writing its redo log files until atime when these writes can be done efficiently

Oracle 10g includes the ability to designate an automatic UNDO tablespace, which assigns the responsibility

for managing rollback segments to the Oracle database itself

Memory Used by an Instance

Figure 1-1, shown previously, includes several areas of memory that are used by an individual Oracleinstance

System Global Area

The System Global Area (SGA) is an area of memory that is accessible to all user processes of an Oracleinstance Three main areas are used by the SGA:

❑ The redo log buffer holds information used for recovery until the information can be written tothe redo log

❑ The shared pool holds information that can be shared across user processes, such as executionplans for SQL statements, compiled stored procedures, and information retrieved from theOracle data dictionary

❑ The database buffer pools are a group of memory areas that are used to hold data blocks A datablock held in a buffer pool can be accessed much more rapidly than going to disk to retrieve the block, so efficient use of these memory pools is essential for achieving optimal performance.Following are the three basic database buffer pools:

❑ The DEFAULT pool holds all database objects, unless otherwise specified

❑ The KEEP pool is used to hold objects in memory if specified for a table or index

❑ The RECYCLE pool is used for objects that are not likely to be reused again.Keep the following two points in mind:

❑ For all of these pools, the Oracle instance uses a Least Recently Used (LRU) algorithm to determine what data blocks to swap out

❑ In addition to these main pools, the Oracle instance can also use a large pool,which is used for shared server, backup and recovery, and I/O operations Youcan either configure a large pool or Oracle can create it automatically, if you configure adaptive parallelism, which is described further in Chapter 2

Program Global Area

The Program Global Area (PGA) is an area of memory that is just available to a single server process.The PGA contains items like user variables and cursor information for an individual user’s SQL state-ment, such as the number of rows that have been retrieved so far The PGA is also used for sorting datafor an individual user process

Each time a new SQL statement is received for a user, a new space in the PGA has to be initialized Toavoid this overhead, transaction-intensive applications, such an online transaction processing (OLTP)applications, typically use a small set of SQL statements that are continually reused by a user process,reducing this potential source of overhead

You can have a single server process handle more than one user process by configuring shared servers, which are described in Chapter 2, “Using SQL.”

The database administrator typically does the memory allocations for these areas, but setting these values inappropriately can have a dramatic affect on the perfor-

mance of your applications Oracle 10g makes it easier to manage these portions of

memory, since it eliminates the need to specify an allocation for the individual

com-ponents of each of these pools With Oracle 10g, you can simply set a maximum size

for the SGA and the PGA, and Oracle will take care of the allocation for the ual components of these areas.

individ-5