Free Oracle Essentials Oracle Database 11g by Rick Greenwald Page A

Java can use the database. ODBC is also supported. Java support includes Java stored procedures and JDBC. The Oracle Lite Database is also designed to be self-tuning and self-administering and is supported on handheld devices running Windows CE, Symbian, Windows, and Linux.
    In typical usage of Oracle Lite, the user will link her handheld or mobile device running the Oracle Lite Database to a large-footprint Oracle Database Server. Data is then automatically synchronized between the two systems. The user will then remove the link and work in disconnected mode. After she has performed her tasks, she will relink and resynchronize the data with the Oracle Database Server.
    Oracle Lite supports a variety of synchronization capabilities, including the following:
    • Bidirectional synchronization between the mobile device and Oracle’s larger footprint databases
    • Publish-and-subscribe based models
    • Support for protocols such as TCP/IP, HTTP, CDPD, 802.1, and HotSync You can define priority-based replication of subsets of data. Because data distributed to multiple locations can lead to conflicts—such as which location now has the
    “true” version of the data—automated conflict and resolution is provided. You can also customize the conflict resolution.
    The Mobile Server provides a single platform for publishing, deploying, synchroniz-ing, and managing mobile applications. The web-based control center can be used for controlling access to mobile applications. Oracle’s former “Web-to-Go” product is also part of the Mobile Server and provides centralized wizard-based application development and deployment.
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    Chapter 1: Introducing Oracle

    Chapter 2
    CHAPTER 2
    Oracle Architecture2
    This chapter focuses on the concepts and structures at the core of the Oracle database. When you understand the architecture of the Oracle server, you’ll have a context for understanding the rest of the features of Oracle described in this book.
    An Oracle database consists of both physical and logical components. The first section of this chapter covers the difference between an Oracle database and an instance, and subsequent sections describe physical components, the instance, and the data dictionary.
    Databases and Instances
    Many Oracle practitioners use the terms instance and database interchangeably. In fact, an instance and a database are different (but related) entities. This distinction is important because it provides insight into Oracle’s architecture.
    In Oracle, the term database refers to the physical storage of information, and the term instance refers to the software executing on the server that provides access to the information in the database. The instance runs on the computer or server; the database is stored on the disks attached to the server. Figure 2-1 illustrates this relationship.
    The database is physical : it consists of files stored on disks. The instance is logical : it consists of in-memory structures and processes on the server. For example, Oracle uses an area of shared memory called the System Global Area (SGA) and a private memory area for each process called the Program Global Area (PGA). An instance can be part of one and only one database, although multiple instances can be part of the same database. Instances are temporal, but databases, with proper maintenance, last forever.
    Users do not directly access the information in an Oracle database. Instead, they pass requests for information to an Oracle instance.
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    Database
    Server
    An Oracle instance consists of
    Oracle Instance
    processes and memory on the
    database server
    An Oracle database consists of physical
    files on the disk
    Oracle Database
    Figure 2-1. An instance and a database
    The real world provides a useful analogy for instances and databases. An instance can be thought of as a bridge to the database, which can be thought of as an island.
    Traffic flows on and off the island via the bridge. If the bridge is closed, the