Arquitectura oracle

The Oracle Architecture

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Chapter 7, “Managing Data with SQL, PL/SQL, and Utilities,” provides information on how to use PL/SQL.

Accessing the Database Using Java
Since its introduction in 1995, Java has emerged as a dominant development environment for web-based applications. The primary reason for Java’s popularity is its operating system independence. Java programs can be developedon one operating system and then deployed on some other operating system without modification. This is made possible by running the Java programs in an operating system–specific engine called the Java Virtual Machine (JVM). In this way, the only part of the Java architecture that is operating system–specific is the JVM—not the programs themselves. By incorporating a JVM directly in the database,Oracle 10g can store and execute compiled Java code natively. This not only greatly improves the performance of Java-based applications, but also allows developers to incorporate Java code directly into PL/SQL procedures, functions, and packages.

Oracle also includes a Java-based driver, the JDBC (Java Database Connectivity) driver, for improved client-to-database Java connectivity.

UsingOracle Programming Interfaces
In addition to SQL, web-based tools, PL/SQL, and Java, Oracle also provides the ability to integrate SQL commands and database connectivity into traditional programming languages such as C, C++, and COBOL. This integration is achieved by using the Oracle precompilers and the Oracle Call Interface (OCI). Oracle precompilers allow programmers to incorporate calls to thedatabase directly into their program code. Precompilers are available for third-generation programming languages such as C and COBOL. The Oracle C++ Call Interface (OCCI) is used with C++ to provide full database interaction with that development environment. The OCCI provides substantial programmatic support for database security and password management, access to Oracle datatypes andobjectrelational features, management of distributed database transactions, and globalization features.

The Oracle Architecture
Each interface described in the previous section allows a user to interact with the database. Using these tools requires that user accounts be created in the database and connectivity to the database be in place across the network. Users must also have adequate storage capacityfor the data that they insert, and they need recovery mechanisms for restoring the transactions that

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Chapter 1

Oracle Database 10g Components and Architecture

they are performing in the event of a hardware failure. As the DBA, you take care of each of these tasks, as well as others, which include the following: Selecting the server hardware on which the database software will runInstalling and configuring the Oracle 10g software on the server hardware Creating the database itself Creating and managing the tables and other objects used to manage the application data Creating and managing database users Establishing reliable backup and recovery processes for the database Monitoring and tuning database performance The remainder of this book is dedicated to helping youunderstand how to perform these and other important Oracle database administration tasks. But, first, to succeed as an Oracle DBA, you need to completely understand Oracle’s underlying architecture and its mechanisms. Understanding the relationship between Oracle’s memory structures, background processes, and I/O activities is critical before learning how to manage these areas. The Oracle Serverarchitecture can be described in three categories: User-related processes Logical memory structures that are collectively called an Oracle instance Physical file structures that are collectively called a database Figure 1.11 shows all the parts of an Oracle instance and database. The architecture in Figure 1.11 may at first seem complex. However, each of these architecture components is described in more...