DatabaseIntroducing Oracle

Introducing Oracle content and product recommendations are editorially independent. We may make money when you click on links to our partners. Learn More.

This is Chapter 1: Introducing Oracle from the book Oracle Essentials : Oracle9i, Oracle8i & Oracle8 (2nd Edition) (ISBN:0-596-00179-7) written by Rick Greenwald, Robert Stackowiak & Jonathan Stern, published by O’Reilly & Associates.

Chapter 1

Introducing Oracle

Where do we start? One of the problems in comprehending a massive product such as the Oracle database is the difficulty of getting a good sense of how the product works without getting lost in the details of implementing specific solutions. This book aims to solve this problem by giving you a thorough grounding in the concepts and technologies that form the foundation of Oracle’s technology products: the Database Server (currently Oracle9i) and the Application Server (Oracle9iAS). Oracle is also a provider of business applications, popularly named the "E-Business Suite"; discussion of those applications is outside the scope of this book, although we do touch on how technology components are being leveraged in linking Oracle’s applications to non-Oracle applications and in building data warehouses.

We’ve tried to write a book for a wide range of Oracle users, from the novice to the experienced user. To address this range of users, we’ve focused on the concepts and technology behind the Oracle database. Once you fully understand these facets of the product, you’ll be able to handle the particulars of virtually any type of Oracle database. Without this understanding, you may feel overburdened as you try to connect the dots of Oracle’s voluminous feature set and documentation.

This first chapter lays the groundwork for the rest of the discussions in this book. Of all the chapters, it covers the broadest range of topics; most of these are discussed further later in the book, but some of the basics–for example, the brief history of Oracle and the contents of the different "flavors" of the Oracle database products–are unique to this chapter.

Oracle has grown from its humble beginnings as one of a number of databases available in the 1970s to the overwhelming market leader of today. In its early days, Oracle Corporation was known as an aggressive sales and promotion organization. Over the years, the Oracle database has grown in depth and quality, and its technical capabilities now match its early hype. With the Oracle8, Oracle8i, and Oracle9i releases, Oracle has added more power and features to its already solid base.

Oracle8, released in 1997, added a host of features (such as the ability to create and store complete objects in the database) and dramatically improved the performance and scalability of the database. Oracle8i, released in 1999, added a new twist to the Oracle database–a combination of enhancements that made the Oracle8i database the focal point of the new world of Internet computing. Oracle9i adds an advanced version of Oracle Parallel Server named Real Application Clusters, along with many additional self-tuning, management, and data warehousing features.

Before we dive into the specific foundations of these new releases, we must spend a little time describing some Oracle basics–how databases evolved to arrive at the relational model, a brief history of Oracle Corporation, and an introduction to the basic features and configurations of the database.

The Evolution of the Relational Database

The concept of the relational database was first described around 1970 by Dr. Edgar F. Codd in an IBM research publication entitled "System R4 Relational." Initially, it was unclear whether any system based on these concepts could achieve commercial success. Nevertheless, Relational Software, Incorporated (RSI) was founded in 1979 and released Oracle V.2 as the world’s first relational database. By 1985, Oracle could claim more than 1,000 relational database customer sites. IBM itself would not embrace relational technology in a commercial product until the Query Management Facility in 1983.

Why has relational database technology grown to become the de facto database technology since that time? A look back at previous database technology may help to explain this phenomenon.

Database management systems were first defined in the 1960s to provide a common organizational framework for what had been data stored in independent files. In 1964, Charles Bachman of General Electric proposed a network model with data records linked together, forming intersecting sets of data, as shown in Figure 1-1. This work formed the basis of the Codasyl Data Base Task Group. Meanwhile, the North American Aviation’s Space Division and IBM developed a second approach based on a hierarchical model in 1965. In this model, data is represented as tree structures in a hierarchy of records, as shown in Figure 1-1. IBM’s product based on this model was brought to market in 1969 as the Information Management System (IMS). As recently as 1980, almost all database implementations used either the network or hierarchical approach. Although several competitors utilized these technologies, only IMS remains.

Figure 1-1.
Network model and hierarchical model


Relational Basics

The relational database uses the concept of linked two-dimensional tables consisting of rows and columns, as shown in Figure 1-2. Unlike the hierarchical approach, no predetermined relationship exists between distinct tables. This means that the data needed to link together the different areas of the network or hierarchical model need not be defined. And because relational users don’t need to understand the representation of data in storage to retrieve it (many such users created ad hoc queries against the data), ease of use helped popularize the relational model.

Figure 1-2.
Relational model with two tables


Relational programming is nonprocedural and operates on a set of rows at a time. In a master-detail relationship between tables, there can be one or many detail rows for each individual master row, yet the statements used to access, insert, or modify the data would simply describe the set of results. In many early relational databases, data access required the use of procedural languages that worked one record at a time. Because of this set orientation, programs can access relational databases more easily.

The contents of the rows in Figure 1-2 are sometimes referred to as records. A column within a row is referred to as a field. Tables are stored in a database schema, which is a logical organizational unit within the database. Other logical structures in the schema often include the following:


Provide a single view of data derived from one or more tables or views. The view is an alternative interface to the data, which is stored in the underlying table(s) that make up the view.


Provide unique numbers for column values.

Stored procedures

Contain logical modules that can be called from programs.


Provide an alternative name for database objects.


Provide faster access to table rows.

Database links

Provide links between distributed databases.

The relationships between columns in different tables are typically described through the use of keys, which are implemented through referential integrity constraints and their supporting indexes. For example, in Figure 1-2, you can establish a link between the DEPTNO column in the second table, which is called a foreign key, to the DEPTNO column in the first table, which is referred to as the primary key of that table.

Finally, even if you define many different indexes for a table, you don’t have to understand them or manage the data they contain. Oracle includes a query optimizer that chooses the best way to use your indexes to access the data for any particular query.

The relational approach lent itself to the Structured Query Language (SQL). SQL was initially defined over a period of years by IBM Research, but it was Oracle Corporation that first introduced it to the market in 1979. SQL was noteworthy at the time for being the only language needed to use relational databases, because you could use SQL:

  • For queries (using a SELECT statement)
  • As a Data Manipulation Language or DML (using INSERT, UPDATE, and DELETE statements)
  • As a Data Definition Language or DDL (using CREATE or DROP statements when adding or deleting tables)
  • To set privileges for users or groups (using GRANT or REVOKE statements)

Today, SQL contains many extensions with ANSI/ISO standards that define its basic syntax.

How Oracle Grew

In 1983, RSI was renamed Oracle Corporation to avoid confusion with a competitor named RTI. At this time, the developers made a critical decision to create a portable version of Oracle (Version 3) that ran not only on Digital VAX/VMS systems, but also on Unix and other platforms. By 1985, Oracle claimed the ability to run on more than 30 platforms (it runs on more than 70 today). Some of these platforms are historical curiosities today, but others remain in use. (In addition to VMS, early operating systems supported by Oracle included IBM MVS, DEC Ultrix, HP/UX, IBM AIX, and Sun’s Solaris version of Unix.) Oracle was able to leverage and accelerate the growth of minicomputers and Unix servers in the 1980s. Today, Oracle leverages its portability on Microsoft Windows NT/2000 and Linux to capture a significant market share on these more recent platforms.

In addition to multiple platform support, other core Oracle messages from the mid-1980s still ring true today, including complementary software development and decision support tools, ANSI standard SQL and portability across platforms, and connectivity over standard networks. Since the mid-1980s, the database deployment model has evolved from dedicated database application servers to client/server to Internet computing implemented with PCs and thin clients accessing database applications via browsers.

Oracle introduced many innovative technical features to the database as computing and deployment models changed (from offering the first distributed database to the first Java Virtual Machine in the core database engine). Table 1-1 presents a short list of Oracle’s major feature introductions.

Table 1-1:
History of Oracle Technology Introductions




Oracle Release 2–the first commercially available relational database to use SQL


Single code base for Oracle across multiple platforms


Portable toolset


Client/server Oracle relational database


CASE and 4GL toolset


Oracle Financial Applications built on relational database




Oracle Parallel Server on massively parallel platforms


Oracle7 with cost-based optimizer


Oracle Version 7.1 generally available: parallel operations including query, load, and create index


Universal database with extended SQL via cartridges, thin client, and application server


Oracle8 generally available: including object-relational and Very Large Database (VLDB) features


Oracle8i generally available: Java Virtual Machine ( JVM) in the database


Oracle9i Application Server generally available: Oracle tools integrated in middle tier


Oracle9i Database Server generally available: Real Application Clusters, Advanced Analytic Services

The Oracle Family

Oracle9i Database Server describes the most recent major version of the Oracle Relational Database Management System (RDBMS) family of products that share common source code. Leveraging predecessors including the Oracle8 release that surfaced in 1997, the family includes:

  • Personal Oracle, a database for single users that’s often used to develop code for implementation on other Oracle multiuser databases
  • Oracle Standard Edition, which was named Workgroup Server in its first iteration as part of the Oracle7 family and is often simply referred to as Oracle Server
  • Oracle Enterprise Edition, which includes additional functionality

In 1998, Oracle announced Oracle8i, which is sometimes referred to as Version 8.1 of the Oracle8 database. The "i " was added to denote added functionality supporting Internet deployment in the new version. Oracle9i followed, with Application Server available in 2000 and Database Server in 2001. The terms "Oracle," "Oracle8," "Oracle8i," and "Oracle9i" may appear to be used somewhat interchangeably in this book, since Oracle9i includes all the features of previous versions. When we describe a new feature that was first made available specifically for Oracle8i or Oracle9i we’ve tried to note that fact to avoid confusion, recognizing that many of you may have old releases of Oracle. We typically use the simple term "Oracle" when describing features that are common to all these releases.

Oracle has focused development around a single source code model since 1983. While each database implementation includes some operating system-specific source code, most of the code is common across the various implementations. The interfaces that users, developers, and administrators deal with for each version are consistent. Features are consistent across platforms for implementations of Oracle Standard Edition and Oracle Enterprise Edition. As a result, companies have been able to migrate Oracle applications easily to various hardware vendors and operating systems while leveraging their investments in Oracle technology. From the company’s perspective, Oracle has been able to focus on implementing new features only once in its product set, instead of having to add functionality at different times to different implementations.

Oracle Standard Edition

When Oracle uses the names Oracle8 Server, Oracle8i Server, or Oracle9i Server to refer to a specific database offering, it refers to what was formerly known as Workgroup Server and is now sometimes called Standard Edition. From a functionality and pricing standpoint, this product intends to compete in the entry-level multiuser and small database category, which supports a smaller numbers of users. These releases are available today on Windows NT, Netware, and Unix platforms such as Compaq (Digital), HP/UX, IBM AIX, Linux, and Sun Solaris.

Oracle Enterprise Edition

Oracle Enterprise Edition is aimed at larger-scale implementations that require additional features. Enterprise Edition is available on far more platforms than the Oracle release for workgroups and includes advanced management, networking, programming, and data warehousing features, as well as a variety of special-purpose options.

Oracle Personal Edition

Oracle Personal Edition is the single-user version of Oracle Enterprise Edition. It is most frequently used by developers because it allows development activities on a single machine. Since the features match those of Enterprise Edition, a developer can write applications using the Personal Edition and deploy them to multiuser servers. Some companies deploy single-user applications using this product. However, Oracle Lite offers a much more lightweight means of deploying the same applications.

Oracle Lite

Oracle Lite, formerly known as Oracle Mobile, is intended for single users who are using wireless devices. It differs from other members of the Oracle database family in that it doesn’t use the same database engine. Instead, Oracle developed a lightweight engine compatible with the limited memory and storage capacity of notebooks and handheld devices. Oracle Lite is described in more detail at the end of this chapter.

Because the SQL supported by Oracle Lite is largely the same as the SQL for other Oracle databases, you can run applications developed for those database engines using Oracle Wireless. Replication of data between Oracle Wireless and other Oracle versions is a key part of most implementations.

Table 1-2 summarizes the situations in which you would typically use each database product. We’ve used the Oracle product names to refer to the different members of the Oracle database family.

Table 1-2:
Oracle Family of Database Products

Database Name

When Appropriate

Oracle Server/

Standard Edition

Version of Oracle server for a small number of users and a smaller database

Oracle Enterprise Edition

Version of Oracle for a large number of users or a large database with advanced features for extensibility, performance, and management

Oracle Personal


Single-user version of Oracle typically used for development of applications for deployment on other Oracle versions

Oracle Lite

Lightweight database engine for mobile computing on notebooks and handheld devices

Summary of Oracle Features

The Oracle database is a broad and powerful product. The remainder of this book examines different aspects of Oracle–for example, data structures, performance, and parallel processing. But before you can understand each of the different areas of Oracle in depth, you must familiarize yourself with the range of features in the Oracle database.

The rest of this chapter gives you a high-level overview of the basic areas of functionality in the Oracle product family. By the end of this chapter, you will at least have some orientation points to guide you in exploring the topics in the rest of this book.

To give some structure to the broad spectrum of the Oracle database, we’ve organized the features into the following sections:

  • Database application development features
  • Database connection features
  • Distributed database features
  • Data movement features
  • Performance features
  • Database management features

At the end of each of the following sections describing database features we’ve included a subsection called "Availability," which indicates the availability of each feature in specific Oracle products. You should be aware that as this feature list grows and Oracle implements packaging changes in new versions, the availability of these features in the version you implement may vary slightly.

In this chapter, we’ve included a lot of terminology and rather abbreviated descriptions of features. Oracle is a huge system. Our goal here is to quickly familiarize you with the full range of features in the system. Subsequent chapters will provide additional details. Obviously, though, whole books can be (and have been!) written about each of the features summarized here.

Database Application Development Features

Applications are often built on the foundation of the Oracle database system. The features of the Oracle database and related products described in this section are used to create applications. We’ve divided the discussion in this section into two categories: database programming and database extensibility options. Later in this chapter, we describe the Internet Developer Suite, a set of optional tools used in Oracle9i Database Server and Oracle9i Application Server development.

Database Programming

All flavors of the Oracle database include different languages and interfaces that allow programmers to access and manipulate the data in the database. Database programming features usually interest two groups: developers building Oracle-based applications that will be sold commercially, and IT organizations within companies that custom-develop applications unique to their businesses. The following sections describe the languages and interfaces supported by Oracle.


The ANSI standard Structured Query Language (SQL) provides basic functions for data manipulation, transaction control, and record retrieval from the database. However, most end users interact with Oracle through applications that provide an interface that hides the underlying SQL and its complexity.


Oracle’s PL/SQL, a procedural language extension to SQL, is commonly used to implement program logic modules for applications. PL/SQL can be used to build stored procedures and triggers, looping controls, conditional statements, and error handling. You can compile and store PL/SQL procedures in the database. You can also execute PL/SQL blocks via SQL*Plus, an interactive tool provided with all versions of Oracle.

Java features and options

Oracle8i introduced the use of Java as a procedural language with a Java Virtual Machine ( JVM) in the database (originally called JServer). JVM includes support for Java stored procedures, methods, triggers, Enterprise JavaBeans? (EJBs), CORBA, IIOP, and HTTP. The Accelerator is used for project generation, translation, and compilation. As of Oracle Version 8.1.7, it can also be used to deploy/install shared libraries.

The inclusion of Java within the Oracle database allows Java developers to leverage their skills as Oracle applications developers. Java applications can be deployed in the client, Oracle9i Application Server, or database, depending on what is most appropriate. We discuss Java development in Chapters 13 and 14.

Large objects

Interest in the use of large objects (LOBs) is growing, particularly for the storage of nontraditional datatypes such as images. The Oracle database has been able to store large objects for some time. Oracle8 added the capability to store multiple LOB columns in each table.

Object-oriented programming

Support of object structures has been included since Oracle8i to provide support for an object-oriented approach to programming. For example, programmers can create user-defined datatypes, complete with their own methods and attributes. Oracle’s object support includes a feature called Object Views through which object-oriented programs can make use of relational data already stored in the database. You can also store objects in the database as varying arrays (VARRAYs), nested tables, or index organized tables (IOTs). We discuss the object-oriented features of Oracle further in Chapter 13.

Third-generation languages (3GLs)

Programmers can interact with the Oracle database from C, C++, Java, COBOL, or FORTRAN applications by embedding SQL in those applications. Prior to compiling the applications using a platform’s native compilers, you must run the embedded SQL code through a precompiler. The precompiler replaces SQL statements with library calls the native compiler can accept. Oracle provides support for this capability through optional "programmer" precompilers for languages such as C and C++ (Pro*C) and COBOL (Pro*COBOL). More recently, Oracle added SQLJ, a precompiler for Java that replaces SQL statements embedded in Java with calls to a SQLJ runtime library, also written in Java.

Database Drivers

All versions of Oracle include database drivers that allow applications to access Oracle via ODBC (the Open DataBase Connectivity standard) or JDBC (the Java DataBase Connectivity open standard).

The Oracle Call Interface

If you’re an experienced programmer seeking optimum performance, you may choose to define SQL statements within host-language character strings and then explicitly parse the statements, bind variables for them, and execute them using the Oracle Call Interface (OCI).

OCI is a much more detailed interface that requires more programmer time and effort to create and debug. Developing an application that uses OCI can be time-consuming, but the added functionality and incremental performance gains often make spending the extra time worthwhile.

Why Use OCI?

Why would someone want to use OCI instead of the higher-level interfaces? In certain programming scenarios, OCI improves application performance or adds functionality. For instance, in high-availability implementations in which multiple systems share disks and implement Real Application Clusters/Oracle Parallel Server, you may want users to reattach to a second server transparently if the first fails. You can write programs that do this using OCI.

National Language Support

National Language Support (NLS) provides character sets and associated functionality, such as date and numeric formats, for a variety of languages. Oracle9i features full Unicode 3.0 support. All data may be stored as Unicode, or select columns may be incrementally stored as Unicode. UTF-8 encoding and UTF-16 encoding provide support for more than 57 languages and 200 character sets. Extensive localization is provided (for example, for data formats) and customized localization can be added through the Oracle Locale Builder.


All of these database programming features are included in both Oracle Standard Edition and Oracle Enterprise Edition.

Database Extensibility

The Internet and corporate intranets have created a growing demand for storage and manipulation of nontraditional datatypes within the database. There is a need for extensions to the standard functionality of a database for storing and manipulating image, audio, video, spatial, and time series information. Oracle8 provides extensibility to the database through options sometimes referred to as cartridges. These options are simply extensions to standard SQL, usually built by Oracle or its partners through C, PL/SQL, or Java. You may find these options helpful if you’re working extensively with the type of data they’re designed to handle.

For more details regarding these features of Oracle, see Chapter 13.

Oracle inter Media

Oracle inter Media bundles what was formerly referred to as the "Context cartridge" for text manipulation with additional image, audio, video, and locator functions and is included in the database license. inter Media offers the following major capabilities:

  • The text portion of inter Media (Oracle9i‘s Oracle Text) can identify the gist of a document by searching for themes and key phrases within the document.
  • The image portion of inter Media can store and retrieve images.
  • The audio and video portions of inter Media can store and retrieve audio and video clips, respectively.
  • The locator portion of inter Media can retrieve data that includes spatial coordinate information.

Oracle Spatial

The Spatial option is available for Oracle Enterprise Edition. It can optimize the display and retrieval of data linked to coordinates and is used in the development of spatial information systems. Several vendors of Geographic Information Systems (GIS) products now bundle this option and leverage it as their search and retrieval engine.

Database Connection Features

The connection between the client and the database server is a key component of the overall architecture of a computing system. The database connection is responsible for supporting all communications between an application and the data it uses. Oracle includes a number of features that establish and tune your database connections.

The following features relate to the way the Oracle database handles the connection between the client and server machines in a database interaction. We’ve divided the discussion in this section into two categories: database networking and Oracle9i Application Server.

Database Networking

Database users connect to the database by establishing a network connection. You can also link database servers via network connections. Oracle provides a number of features to establish connections between users and the database and/or between database servers, as described in the following sections.

Oracle Net/Net8

Oracle’s network interface, Net8, was formerly known as SQL*Net when used with Oracle7 and previous versions of Oracle. You can use Net8 over a wide variety of network protocols, although TCP/IP is by far the most common protocol today.

In Oracle9i, the name of Net8 has been changed to Oracle Net, and the features associated with Net8, such as shared servers, are referred to as Oracle Net Services.

Oracle Names

Oracle Names allows clients to connect to an Oracle server without requiring a configuration file on each client. Using Oracle Names can reduce maintenance efforts, since a change in the topology of your network will not require a corresponding change in configuration files on every client machine.

Oracle Internet Directory

The Oracle Internet Directory (OID) was introduced with Oracle8i. OID serves the same function as Oracle Names in that it gives users a way to connect to an Oracle Server without having a client-side configuration file. However, OID differs from Oracle Names in that it is an LDAP (Lightweight Directory Access Protocol) directory; it does not merely support the Oracle-only Oracle Net/Net8 protocol.

Oracle Connection Manager

Each connection to the database takes up valuable network resources, which can impact the overall performance of a database application. Oracle’s Connection Manager, illustrated in Figure 1-3, reduces the number of network connections to the database through the use of concentrators, which provide connection multiplexing to implement multiple connections over a single network connection. Connection multiplexing provides the greatest benefit when there are a large number of active users.

Figure 1-3.
Concentrators with Connection Managers for a large number of users


You can also use the Connection Manager to provide multiprotocol connectivity when clients and servers run different network protocols. This capability replaces the multiprotocol interchange formerly offered by Oracle, but it is less important today because many companies now use TCP/IP as their standard protocol.

Advanced Security Option

Advanced Security, now available as an option, was formerly known as the Advanced Networking Option (ANO). Key features include network encryption services using RSA Data Security’s RC4 or DES algorithm, network data integrity checking, enhanced authentication integration, single sign-on, and DCE (Distributed Computing Environment) integration.


Advanced networking features such as the Oracle Connection Manager and the Advanced Security Option have typically been available for the Enterprise Edition of the database, but not for the Standard Edition.

Oracle9i Application Server

The popularity of Internet and intranet applications has led to a change in deployment from client/server (with fat clients running a significant piece of the application) to a three-tier architecture (with a browser supplying everything needed on a thin client). Oracle9i Application Server (Oracle9iAS) provides a means of implementing the middle tier of a three-tier solution for web-based applications, component-based applications, and enterprise application integration. Oracle9iAS replaces Oracle Application Server (OAS) and Oracle Web Application Server. Oracle9iAS can be scaled across multiple middle-tier servers.

This product includes a web listener based on the popular Apache listener, servlets and JavaServer Pages ( JSPs), business logic, and/or data access components. Business logic might include JavaBeans, Business Components for Java (BC4J), and Enterprise JavaBeans (EJBs). Data access components can include JDBC, SQLJ, BC4J, and EJBs.

Oracle9iAS offers additional solutions in the cache, portal, intelligence, and wireless areas:


Oracle9iAS Database Cache provides a middle tier for the caching of PL/SQL procedures and anonymous PL/SQL blocks.


Oracle9iAS Portal is part of the Internet Developer Suite (discussed later in this chapter) and is used for building easy-to-use browser interfaces to applications through servlets and HTTP links. The developed portal is deployed to Oracle9iAS.


Oracle9iAS Intelligence often includes Oracle9iAS Portal, but also consists of:

  • Oracle Reports, which provides a scalable middle tier for the reporting of prebuilt query results
  • Oracle Discoverer, for ad hoc query and relational online analytical processing (ROLAP)
  • OLAP applications custom-built with JDeveloper
  • Business intelligence beans that leverage Oracle9i Advanced Analytic Services
  • Clickstream Intelligence
  • These capabilities are discussed in Chapter 9.

    Oracle Wireless Edition (formerly known as Oracle Portal-to-Go) includes:

  • Content adapters for transforming content to XML
  • Device transformers for transforming XML to device-specific markup languages
  • Personalization portals for service personalization of alerts, alert addresses, location marks, and profiles; the wireless personalization portal is also used for the creation, servicing, testing, and publishing of URL service and for user management
  • Figure 1-4 shows many of the connection possibilities we’ve discussed.

    Figure 1-4.
    Typical Oracle database connections



    Because Oracle9iAS is a separate product, it can be used with various versions of the Oracle8i and Oracle9i database and with either edition.

    Oracle9iAS itself also is packaged in a Standard Edition and an Enterprise Edition. Features requiring Enterprise Edition include Cache, PL/SQL, Forms Services, Reports Services, Discoverer Viewer, Oracle Internet Directory, Oracle Workflow, Oracle Application Interconnect, and Oracle Enterprise Manager Management Server. For more details about Oracle9iAS, see Chapter 14.

    Distributed Database Features

    One of the strongest features of the Oracle database is its ability to scale up to handle extremely large volumes of data and users. Oracle scales not only by running on more and more powerful platforms, but also by running in a distributed configuration. Oracle databases on separate platforms can be combined to act as a single logical distributed database.

    This section describes some of the basic ways that Oracle handles database interactions in a distributed database system.

    Distributed Queries and Transactions

    Data within an organization is often spread among multiple databases for reasons of both capacity and organizational responsibility. Users may want to query this distributed data or update it as if it existed within a single database.

    Oracle first introduced distributed databases in response to the requirements for accessing data on multiple platforms in the early 1980s. Distributed queries can retrieve data from multiple databases. Distributed transactions can insert, update, or delete data on distributed databases. Oracle’s two-phase commit mechanism, which is described in detail in Chapter 12, guarantees that all the database servers that are part of a transaction will either commit or roll back the transaction. Distributed transactions that may be interrupted by a system failure are monitored by a recovery background process. Once the failed system comes back online, the same process will complete the distributed transactions to maintain consistency across the databases.

    You can also implement distributed transactions in Oracle by popular transaction monitors (TPs) that interact with Oracle via XA, an industry standard (X/Open) interface. Oracle8i also added native transaction coordination with the Microsoft Transaction Server (MTS), so you can implement a distributed transaction initiated under the control of MTS through an Oracle database.

    Heterogeneous Services

    Heterogeneous Services allow non-Oracle data and services to be accessed from an Oracle database through tools such as Oracle Transparent Gateways. For example, Transparent Gateways allow users to submit Oracle SQL statements to a non-Oracle distributed database source and have them automatically translated into the SQL dialect of the non-Oracle source system, which remains transparent to the user. In addition to providing underlying SQL services, Heterogeneous Services provide transaction services utilizing Oracle’s two-phase commit with non-Oracle databases and procedural services that call third-generation language routines on non-Oracle systems. Users interact with the Oracle database as if all objects are stored in the Oracle database, and Heterogeneous Services handle the transparent interaction with the foreign database on the user’s behalf.

    Heterogeneous Services work in conjunction with Transparent Gateways. Generic connectivity via ODBC and OLEDB is included with the database. Optional Transparent Gateways use agents specifically tailored for a variety of target systems.


    All the technologies discussed in this section are included in both editions of the database.

    Data Movement Features

    Moving data from one Oracle database to another is often a requirement when using distributed databases, or when a user wants to implement multiple copies of the same database in multiple locations to reduce network traffic or increase data availability. You can export data and data dictionaries (metadata) from one database and import them into another. Oracle also offers many other advanced features in this category, including replication, transportable tablespaces, and Advanced Queuing.

    This section describes the technology used to move data from one Oracle database to another automatically.

    Basic Replication

    You can use basic replication to move recently added and updated data from an Oracle "master" database to databases on which duplicate sets of data reside. In basic replication, only the single master is updated. You can manage replication through the Oracle Enterprise Manager (OEM prior to Oracle9i, EM in Oracle9i).

    Advanced Replication

    You can use advanced replication in multimaster systems in which any of the databases involved can be updated and conflict-resolution features are needed to resolve inconsistencies in the data. Because there is more than one master database, the same data may be updated on multiple systems at the same time. Conflict resolution is necessary to determine the "true" version of the data. Oracle’s advanced replication includes a number of conflict-resolution scenarios and also allows programmers to write their own. We cover replication in more detail in Chapter 12.

    Transportable Tablespaces

    Transportable tablespaces were introduced in Oracle8i. Instead of using the export/import process, which dumps data and the structures that contain it into an intermediate file for loading, you simply put the tablespaces in read-only mode, move or copy them from one database to another, and mount them. You must export the data dictionary (metadata) for the tablespace from the source and import it at the target. This feature can save a lot of time during maintenance, because it simplifies the process.

    Advanced Queuing

    Advanced Queuing (AQ), introduced in Oracle8, provides the means to asynchronously send messages from one Oracle database to another. Because messages are stored in a queue in the database and sent asynchronously when the connection is made, the amount of overhead and network traffic is much lower than it would be using traditional guaranteed delivery through the two-phase commit protocol between source and target. By storing the messages in the database, AQ provides a solution with greater recoverability than other queuing solutions that store messages in filesystems.

    Oracle messaging adds the capability to develop and deploy a contentbased publish and subscribe solution using a rules engine to determine relevant subscribing applications. As new content is published to a subscriber list, the rules on the list determine which subscribers should receive the content. This approach means that a single list can efficiently serve the needs of different subscriber communities.

    Oracle9i AQ adds XML support and Oracle Internet Directory (OID) integration. This technology is leveraged in Oracle Application Interconnect (OAI), which includes adapters to non-Oracle applications, messaging products, and databases.


    Although basic replication has been included with both Oracle Standard Edition and Enterprise Edition, advanced features such as advanced replication, transportable tablespaces, and Advanced Queuing have typically required Enterprise Edition.

    Performance Features

    Oracle includes several features specifically designed to boost performance in certain situations. We’ve divided the discussion in this section into two categories: database parallelization and data warehousing.

    Database Parallelization

    Database tasks implemented in parallel speed up querying, tuning, and maintenance of the database. By breaking up a single task into smaller tasks and assigning each subtask to an independent process, you can dramatically improve the performance of certain types of database operations.

    Parallel query features became a standard part of Enterprise Edition beginning with Oracle 7.3. Examples of query features implemented in parallel include:

    • Table scans
    • Nested loops
    • Sort merge joins
    • GROUP BYs
    • NOT IN subqueries (anti-joins)
    • User-defined functions
    • Index scans
    • Select distinct UNION and UNION ALL
    • Hash joins
    • ORDER BY and aggregation
    • Bitmap star joins
    • Partition-wise joins
    • Stored procedures (PL/SQL, Java, external routines)

    When you’re using Oracle, by default the degree of parallelism for any operation is set to twice the number of CPUs. You can adjust this degree automatically for each subsequent query based on the system load. You can also generate statistics for the cost-based optimizer in parallel.


    You can perform maintenance functions such as loading (via SQL*Loader), backups, and index builds in parallel in Oracle Enterprise Edition. Oracle Partitioning for the Enterprise Edition enables additional parallel Data Manipulation Language (DML) inserts, updates, and deletes as well as index scans.

    Data Warehousing

    The parallel features discussed in the previous section improve the overall performance of the Oracle database. Oracle has also added some performance enhancements that specifically apply to data warehousing applications. For detailed explanations of these and complementary products and features related to data warehousing, see Chapter 9.

    Bitmap indexes

    Oracle added support for stored bitmap indexes to Oracle 7.3 to provide a fast way of selecting and retrieving certain types of data. Bitmap indexes typically work best for columns that have few different values relative to the overall number of rows in a table.

    Rather than storing the actual value, a bitmap index uses an individual bit for each potential value with the bit either "on" (set to 1) to indicate that the row contains the value or "off" (set to 0) to indicate that the row does not contain the value. This storage mechanism can also provide performance improvements for the types of joins typically used in data warehousing. Bitmap indexes are described in more detail in Chapter 4.

    Star query optimization

    Typical data warehousing queries occur against a large fact table with foreign keys to much smaller dimension tables. Oracle added an optimization for this type of star query to Oracle 7.3. (See Figure 9-2 for an illustration of a typical star schema.) Performance gains are realized through the use of Cartesian product joins of dimension tables with a single join back to the large fact table. Oracle8 introduced a further mechanism called a parallel bitmap star join, which uses bitmap indexes on the foreign keys to the dimension tables to speed star joins involving a large number of dimension tables.

    Materialized views

    In Oracle, materialized views provide another means of achieving a significant speed-up of query performance. Summary-level information derived from a fact table and grouped along dimension values is stored as a materialized view. Queries that can use this view are directed to the view, transparently to the user and the SQL they submit.

    Analytic functions

    A growing trend in Oracle and other systems is the movement of some functions from decision-support user tools into the database. Oracle8i and Oracle9i feature the addition of ANSI standard OLAP SQL analytic functions for windowing, statistics, CUBE and ROLLUP, and more.

    Oracle9i Advanced Analytic Services

    Oracle9i Advanced Analytic Services are a combination of what used to be called OLAP Services and Data Mining. The OLAP services provide a Java OLAP API and are typically leveraged to build custom OLAP applications through the use of Oracle’s JDeveloper product. Oracle9i Advanced Analytic Services in the database also provide predictive OLAP functions and a multidimensional cache for doing the same kinds of analysis previously possible in Oracle’s Express Server.

    The Oracle9i database engine also includes data-mining algorithms that are exposed through a Java data-mining API.


    Oracle Standard Edition lacks many important data warehousing features available in the Enterprise Edition, such as bitmap indexes and materialized views. Hence, use of Enterprise Edition is recommended for data warehousing projects.

    Database Management Features

    Oracle includes many features that make the database easier to manage. We’ve divided the discussion in this section into four categories: Oracle Enterprise Manager, add-on packs, backup and recovery, and database availability.

    Oracle Enterprise Manager

    As part of every Database Server, Oracle provides the Oracle Enterprise Manager (EM), a database management tool framework with a graphical interface used to manage database users, instances, and features (such as replication) that can provide additional information about the Oracle environment. EM can also manage Oracle9iAS and Oracle iFS, Internet Directory, and Express.

    Prior to the Oracle8i database, the EM software had to be installed on Windows 95/98 or NT-based systems and each repository could be accessed by only a single database manager at a time. Now you can use EM from a browser or load it onto Windows 95/98/2000 or NT-based systems. Multiple database administrators can access the EM repository at the same time. In the EM release for Oracle9i, the super administrator can define services that should be displayed on other administrators’ consoles, and management regions can be set up.

    Add-on Packs

    Several optional add-on packs are available for Oracle, as described in the following sections and in more detail in Chapter 5. In addition to these database-management packs, management packs are available for Oracle Applications and for SAP R/3.

    Standard Management Pack

    The Standard Management Pack for Oracle provides tools for the management of small Oracle databases (e.g., Oracle Server/Standard Edition). Features include support for performance monitoring of database contention, I/O, load, memory use and instance metrics, session analysis, index tuning, and change investigation and tracking.

    Diagnostics Pack

    You can use the Diagnostics Pack to monitor, diagnose, and maintain the health of Enterprise Edition databases, operating systems, and applications. With both historical and real-time analysis, you can automatically avoid problems before they occur. The pack also provides capacity planning features that help you plan and track future system-resource requirements.

    Tuning Pack

    With the Tuning Pack, you can optimize system performance by identifying and tuning Enterprise Edition database and application bottlenecks such as inefficient SQL, poor data design, and the improper use of system resources. The pack can proactively discover tuning opportunities and automatically generate the analysis and required changes to tune the system.

    Change Management Pack

    The Change Management Pack helps eliminate errors and loss of data when upgrading Enterprise Edition databases to support new applications. It can analyze the impact and complex dependencies associated with application changes and automatically perform database upgrades. Users can initiate changes with easy-to-use wizards that teach the systematic steps necessary to upgrade.


    Oracle Enterprise Manager can be used for managing Oracle Standard Edition and/or Enterprise Edition. Additional functionality for diagnostics, tuning, and change management of Standard Edition instances is provided by the Standard Management Pack. For Enterprise Edition, such additional functionality is provided by separate Diagnostics, Tuning, and Change Management Packs.

    Backup and Recovery

    As every database administrator knows, backing up a database is a rather mundane but necessary task. An improper backup makes recovery difficult, if not impossible. Unfortunately, people often realize the extreme importance of this everyday task only when it is too late–usually after losing business-critical data due to a failure of a related system.

    The following sections describe some products and techniques for performing database backup operations. We discuss backup and recovery strategies and options in much greater detail in Chapter 10.

    Recovery Manager

    Typical backups include complete database backups (the most common type), tablespace backups, datafile backups, control file backups, and archivelog backups. Oracle8 introduced the Recovery Manager (RMAN) for the server-managed backup and recovery of the database. Previously, Oracle’s Enterprise Backup Utility (EBU) provided a similar solution on some platforms. However, RMAN, with its Recovery Catalog stored in an Oracle database, provides a much more complete solution. RMAN can automatically locate, back up, restore, and recover datafiles, control files, and archived redo logs. RMAN for Oracle9i can restart backups and restores and implement recovery window policies when backups expire. The Oracle Enterprise Manager Backup Manager provides a GUI-based interface to RMAN.

    Incremental backup and recovery

    RMAN can perform incremental backups of Enterprise Edition databases. Incremental backups back up only the blocks modified since the last backup of a datafile, tablespace, or database; thus, they’re smaller and faster than complete backups. RMAN can also perform point-in-time recovery, which allows the recovery of data until just prior to a undesirable event (such as the mistaken dropping of a table).

    Legato Storage Manager

    Various media-management software vendors support RMAN. Oracle bundles Legato Storage Manager with Oracle to provide media-management services, including the tracking of tape volumes, for up to four devices. RMAN interfaces automatically with the media-management software to request the mounting of tapes as needed for backup and recovery operations.


    While basic recovery facilities are available for both Oracle Standard Edition and Enterprise Edition, incremental backups have typically been limited to Enterprise Edition.

    Database Availability

    Database availability depends upon the reliability and management of the database, the underlying operating system, and the specific hardware components of the system. Oracle has improved availability by reducing backup and recovery times. It has done this through:

    • Providing online and parallel backup and recovery
    • Improving the management of online data through range partitioning
    • Leveraging hardware capabilities for improved monitoring and failover

    The relevant features are described in the following sections.

    Partitioning option

    Oracle introduced partitioning as an option to Oracle8 to provide a higher degree of manageability and availability. You can take individual partitions offline for maintenance while other partitions remain available for user access. In data warehousing implementations, partitioning is frequently used to implement rolling windows based on date ranges. Hash partitioning, in which the data partitions are divided up as a result of a hashing function, was added to Oracle8i to enable an even distribution of data. You can also use composite partitioning to enable hash subpartitioning within specific range partitions. Oracle9i adds list partitioning, which enables the partitioning of data based on discrete values such as geography.

    Oracle9i Data Guard

    Oracle first introduced a standby database feature in Oracle 7.3. The standby database provides a copy of the production database to be used if the primary database is lost–for example, in the event of primary site failure, or during routine maintenance. Primary and standby databases may be geographically separated. The standby database is created from a copy of the production database and updated through the application of archived redo logs generated by the production database. The Oracle9i Data Guard product fully automates this process; previously, you had to manually copy and apply the logs. Agents are deployed on both the production and standby database, and a Data Guard Broker coordinates commands. A single Data Guard command is used to run the eight steps required for failover.

    In addition to providing physical standby database support, Oracle9i Data Guard (second release) will be able to create a logical standby database. In this scenario, Oracle archive logs are transformed into SQL transactions and applied to an open standby database.

    Failover features and options

    The failover feature provides a higher level of reliability for an Oracle database. Failover is implemented through a second system or node that provides access to data residing on a shared disk when the first system or node fails. Oracle Fail Safe for Windows NT/2000, in combination with Microsoft Cluster Services, provides a failover solution in the event of a system failure. Unix systems such as HP-UX and Solaris have long provided similar functionality for their clusters.

    Oracle Parallel Server/Real Application Clusters failover features

    The Oracle Parallel Server (OPS) option, renamed Real Application Clusters in Oracle9i, can provide failover support as well as increased scalability on Unix and Windows NT clusters. Oracle8i greatly improved scalability for read/write applications through the introduction of Cache Fusion. Oracle9i improved Cache Fusion for write/write applications by further minimizing much of the disk write activity used to control data locking.

    With Real Application Clusters, you can run multiple Oracle instances on systems in a shared disk cluster configuration or on multiple nodes of a Massively Parallel Processor (MPP) configuration. The Real Application Cluster coordinates traffic among the systems or nodes, allowing the instances to function as a single database. As a result, the database can scale across hundreds of nodes. Since the cluster provides a means by which multiple instances can access the same data, the failure of a single instance will not cause extensive delays while the system recovers; you can simply redirect users to another instance that’s still operating. You can write applications with the Oracle Call Interface (OCI) to provide failover to a second instance transparently to the user.

    Parallel Fail Safe/RACGuard

    Parallel Fail Safe, renamed RACGuard in Oracle9i, provides automated failover with bounded recovery time in conjunction with Oracle Parallel Server/Real Application Clusters. In addition, Parallel Fail Safe provides client rerouting from the failed instance to the instance that is available with fast reconnect and automatically captures diagnostic data.


    Advanced high-availability features such as the Partitioning option and Real Application Clusters have typically been available for Oracle Enterprise Edition but not for Standard Edition.

    Oracle Internet Developer Suite

    Many Oracle tools are available to developers to help them present data and build more sophisticated Oracle database applications. Although this book focuses on the Oracle database, this section briefly describes the main Oracle tools for application development: Oracle Forms Developer, Oracle Reports Developer, Oracle Designer, Oracle JDeveloper, Oracle Discoverer Administrative Edition, and Oracle Portal.

    Oracle Forms Developer

    Oracle Forms Developer provides a powerful tool for building forms-based applications and charts for deployment as traditional client/server applications or as three-tier browser-based applications via Oracle9i Application Server. Developer is a fourth-generation language (4GL). With a 4GL, you define applications by defining values for properties, rather than by writing procedural code. Developer supports a wide variety of clients, including traditional client/server PCs and Java-based clients. Version 6 of Developer adds more options for creating easier-to-use applications, including support for animated controls in user dialogs and enhanced user controls. The Forms Builder in Version 6 includes a built-in JVM for previewing web applications.

    Oracle Reports Developer

    Oracle Reports Developer provides a development and deployment environment for rapidly building and publishing web-based reports via Reports for Oracle9i Application Server. Data can be formatted in tables, matrices, group reports, graphs, and combinations. High-quality presentation is possible using the HTML extension Cascading Style Sheets (CSS).

    Oracle JDeveloper

    Oracle JDeveloper was introduced by Oracle in 1998 to develop basic Java applications without writing code. JDeveloper includes a Data Form wizard, a BeansExpress wizard for creating JavaBeans and BeanInfo classes, and a Deployment wizard. JDeveloper includes database development features such as various Oracle drivers, a Connection Editor to hide the JDBC API complexity, database components to bind visual controls, and a SQLJ precompiler for embedding SQL in Java code, which you can then use with Oracle. You can also deploy applications developed with JDeveloper using the Oracle9i Application Server. Although JDeveloper uses wizards to allow programmers to create Java objects without writing code, the end result is generated Java code. This Java implementation makes the code highly flexible, but it is typically a less productive development environment than a true 4GL.

    Oracle Designer

    Oracle Designer provides a graphical interface for Rapid Application Development (RAD) for the entire database development process–from building the business model to schema design, generation, and deployment. Designs and changes are stored in a multiuser repository. The tool can reverse-engineer existing tables and database schemas for reuse and redesign from Oracle and non-Oracle relational databases.

    Designer also includes generators for creating applications for Oracle Developer, HTML clients using Oracle9i Application Server, and C++. Designer can generate applications and reverse-engineer existing applications or applications that have been modified by developers. This capability enables a process called round-trip engineering, in which a developer uses Designer to generate an application, modifies the generated application, and reverse-engineers the changes back into the Designer repository.

    Oracle Discoverer Administration Edition

    Oracle Discoverer Administration Edition enables administrators to set up and maintain the Discoverer End User Layer (EUL). The purpose of this layer is to shield business analysts using Discoverer as an ad hoc query or ROLAP tool from SQL complexity. Wizards guide the administrator through the process of building the EUL. In addition, administrators can put limits on resources available to analysts monitored by the Discoverer query governor.

    Oracle9iAS Portal

    Oracle9iAS Portal, introduced as WebDB in 1999, provides an HTML-based tool for developing web-enabled applications and content-driven web sites. Portal application systems are developed and deployed in a simple browser environment. Portal includes wizards for developing application components incorporating "servlets" and access to other HTTP web sites. For example, Oracle Reports and Discoverer may be accessed as servlets. Portals can be designed to be user-customizable. They are deployed to the middle-tier Oracle9i Application Server.

    The main enhancement that Oracle9iAS Portal brings to WebDB is the ability to create and use portlets, which allow a single web page to be divided up into different areas that can independently display information and interact with the user.


    All of these pieces are bundled in the Internet Developer Suite. The Internet Developer Suite is an option.

    Oracle Lite

    Oracle Lite is Oracle’s suite of products for enabling mobile use of database-centric applications. Key components of Oracle Lite include the Oracle Lite database and iConnect, which consists of Advanced Replication, Oracle Mobile Agents (OMA), Oracle Lite Consolidator for Palm, and Oracle AQ Lite.

    Although the Oracle Lite database engine can operate with much less memory than other Oracle implementations (it requires less than 1 MB of memory to run on a laptop), Oracle SQL, C and C++, and Java-based applications can run against the database. Java support includes support of Java stored procedures, JDBC, and SQLJ. The database is self-tuning and self-administering. In addition to Windows-based laptops, Oracle Lite is also supported on handheld devices running WindowsCE and Palm OS.

    A variety of replication possibilities exist between Oracle and Oracle Lite, including the following:

    • Connection-based replication via Oracle Net, Net8, or SQL*Net synchronous connections
    • Wireless replication through the use of Advanced Queuing Lite, which provides a messaging service compatible with Oracle Advanced Queuing (and replaces the Oracle Mobile Agents capability available in previous versions of Oracle Lite)
    • File-based replication via standards such as FTP and MAPI
    • Internet replication via HTTP or MIME

    You can define replication of subsets of data via SQL statements. Because data distributed to multiple locations can lead to conflicts–such as which location now has the "true" version of the data–multiple conflict and resolution algorithms are provided. Alternatively, you can write your own algorithm.

    In typical usage of Oracle Lite, the user will link her handheld or mobile device running Oracle Lite to an Oracle Database Server. Data and applications will be synchronized between the two systems. The user will then remove the link and work in disconnected mode. After she has performed her tasks, she’ll relink and resynchronize the data with the Oracle Database Server.

    About the Authors

    Rick Greenwald has been active in the world of computer software for nearly two decades, including stints with Data General, Cognos, and Gupta. He is currently an analyst with Oracle Corporation. He has been a principal author of ten books and countless articles on a variety of technical topics, and has spoken at conferences and training sessions across six continents. In addition to Oracle in a Nutshell, Rick’s books include Oracle Essentials: Oracle9i, Oracle8i, and Oracle8 (principal author with Robert Stackowiak and Jonathan Stern, O’Reilly & Associates, 2001), Oracle Power Objects Developer’s Guide (principal author with Kasu Sista and Richard Finklestein, Oracle Press, 1995); Mastering Oracle Power Objects (principal author with Robert Hoskins, O’Reilly & Associates, 1996); Using Oracle Web Server (principal author with many others, Que Publishing, 1997); The Oracle WebDB Bible (principal author with Jim Milbery, IDG Books Worldwide, 1999); and Administering Exchange Server (principal author with Walter Glenn, Microsoft Press, 1999).

    Robert Stackowiak has worked for 20 years in IT industry related roles that have included software development, management of software development, systems engineering, sales and sales consulting, and business development. He currently is recognized worldwide as a field sales expert in data warehousing at Oracle, and previously was well recognized for his work at IBM’s RISC System/6000 Division, Harris Computer Systems, and the U.S. Army Corps of Engineers. Bob has spoken at numerous computer related conferences and has conducted briefings with companies based around the world. His papers regarding data warehousing and computer and software technology have appeared in publications such as The Data Warehousing Institute’s Journal of Data Warehousing, Informix Tech Notes, and AIXcellence Magazine. Robert’s books include Oracle Power Objects Developer’s Guide, principal author with Kasu Sista and Richard Finklestein (Oracle Press, 1995); Mastering Oracle Power Objects, principal author with Robert Hoskins (O’Reilly & Associates, 1996); Special Edition: Using Oracle Web Server, principal author with many others (Que Publishing, 1997); The Oracle WebDB Bible, principal author with Jim Milbery (IDG Books Worldwide, 1999); and Administering Exchange Server, principal author with Walter Glenn (1999)

    Jonathan Stern has over 11 years of IT experience, including senior positions in consulting, systems architecture, and technical sales. He has in-depth experience with the Oracle RDBMS across all major open systems hardware and operating systems, covering tuning, scaling and parallelism, Parallel Server, high availability, data warehousing, OLTP, object-relational databases, N-tier architectures, and emerging trends such as Java and CORBA. He is the Central USA Technical Team Leader at Ariba, Inc., the leading vendor of electronic commerce solutions for strategic procurement. Previously, he led a team of highly experienced database specialists at Oracle Corporation providing technical depth and strategic assistance to Oracle’s largest customers in the North Central USA. Jonathan has authored papers and presented at internal and external conferences on topics such as scaling with Oracle’s dynamic parallelism and the role of reorganizing segments in an Oracle database.

    Source of this material

    This is Chapter 1: Introducing Oracle from the book Oracle Essentials : Oracle9i, Oracle8i & Oracle8 (2nd Edition) (ISBN:0-596-00179-7) written by Rick Greenwald, Robert Stackowiak & Jonathan Stern, published by O’Reilly & Associates.

    To access the full Table of Contents for the book

    Get the Free Newsletter!

    Subscribe to Developer Insider for top news, trends & analysis

    Latest Posts

    Related Stories