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Overview of Oracle – Part I

Posted by Ravi Varma Thumati on October 12, 2009

Database Management

Excellent Book keeping strategies existed before the computer age, on the management of data, including convenient and efficient retrieval and update operations. But, because of the limitations associated with the physical handling of documents and human processing, a look in retrospect suggests that data (and information generated through data) were only marginally used in daily decision-making, even in progressive organizations.

The application of computers speeds up the data processing activities and adds some flexibility to the management of data and the information generated from it. Widespread and easy access to time sharing systems, advances in logical and physical access methods matched by steep increases in the density and volume of disk storage devices, led gradually to a reassessment of the role of data in management decision making.

This transition was facilitated by the induction of database technology into the organizations.

Approaches to Data Management

Manual methods of Data Management

  • Convenient and efficient retrieval
  • Updating Operations

Limitation of Manual Data Management

  • Physical Volume Data
  • Human Processing of Data

Technological Advancement in Data Management

  • Using Computers to speedup processing of Data
  • Advancement of Processing Power
  • Using time-sharing for multiple users
  • High-speed for multiple users
  • Centralized to distributed databases
  • Centralized to distributed Processing (Client/Server)

Database Management System

The evolution of database management was accompanied and promoted by Advances in computing: Hardware, OS and Networking

Drawbacks of the prevalent approach to data management

  • Data Redundancy
  • Risk to data integrity
  • Data isolation
  • Difficult access to data
  • Unsatisfactory security measures
  • Poor support of concurrent access of data

Before knowing about Oracle we must know about what is Database Management System (DBMS). A Database Management System is essentially a collection of interrelated data and a set of programs to access this data. This collection of data is called Database Management System. The primary objective of a DBMS is to provide a convenient environment to retrieve and store database information. Database

Management System supports only Single user environment.

Database Models

  • Hierarchical
  • Network
  • Relational

Hierarchical Model

This model was introduced in the Information Management System (IMS) developed by IBM in 1968. This model is like a hierarchical tree structure, used to construct a hierarchy of records in the form of nodes and branches. The data elements present in the structure have Parent-Child relationship. Closely related information in the parent-child structure is stored together as a logical unit. A parent unit may have many child units, but a child is restricted to have only one parent.

The drawbacks of this model are:

  • The hierarchical structure is not flexible to represent all the relationship proportions, which occur in the real world.
  • It cannot demonstrate the overall data model for the enterprise because of the non-availability of actual data at the time of designing the data model.
  • It cannot represent the Many-to-Many relationship.

Network Model

It supports the One-To-One and One-To-Many types only. The basic objects in this model are Data Items, Data Aggregates, Records and Sets.

It is an improvement on the Hierarchical Model. Here multiple parent-child relationships are used. Rapid and easy access to data is possible in this model due to multiple access paths to the data elements.

Relational Model

  • Does not maintain physical connection between relations
  • Data is organized in terms of rows and columns in a table
  • The position of a row and/or column in a table is of no importance
  • The intersection of a row and column must give a single value
  • Features of an RDBMS
    • The ability to create multiple relations and enter data into them
    • An attractive query language
    • Retrieval of information stored in more than one table
  • An RDBMS product has to satisfy at least seven of the 12 rules of Codd to be accepted as a full-fledged RDBMS.

Relational Database Management System

RDBMS is acronym for Relation Database Management System. Dr. E. F. Codd first introduced the Relational Database Model in 1970. The Relational model allows data to be represented in a simple rowcolumn.

Each data field is considered as a column and each record is considered as a row. Relational Database is more or less similar to Database Management System. In relational model there is relation between their data elements. Data is stored in tables. Tables have columns, rows and names. Tables can be related to each other if each has a column with a common type of information. The most famous RDBMS packages are Oracle, Sybase, SQL Server and Informix.

Simple example of Relational model is as follows:

oracle1

Here, both tables are based on student’s details. Common field in both tables is Rollno. So we can say both tables are related with each other through Rollno column.

Degree of Relationship

  • One to One (1:1)
  • One to Many or Many to One (1:M / M: 1)
  • Many to Many (M: M)

The Degree of Relationship indicates the link between two entities for a specified occurrence of each.

 One to One Relationship: (1:1)oracle2

One student has only one Rollno

For one occurrence of the first entity, there can be, at the most one related occurrence of the second entity, and vice-versa.

One to Many or Many to One Relationship: (1: M/M: 1)

oracle3

As per the Institutions Norm, One student can enroll in one course at a time however, in one course; here can be more than one student.

For one occurrence of the first entity there can exists many related occurrences of the second entity and for every occurrence of the second entity there exists only one associated occurrence of the first.

Many to Many Relationship: (M:M)

 oracle4

The major disadvantage of the relational model is that a clear-cut interface cannot be determined. Reusability of a structure is not possible. The Relational Database now accepted model on which major database system are built. Oracle has introduced added functionality to this by incorporated object-oriented capabilities. Now it is known is as Object Relational Database Management System (ORDBMS). Objectoriented concept is added in Oracle8.

Some basic rules have to be followed for a DBMS to be relational. They are known as Codd’s rules, designed in such a way that when the database is ready for use it encapsulates the relational theory to its full potential. These twelve rules are as follows.

E. F. Codd Rules

  • The Information Rule: All information must be store in table as data values.
  • The Rule of Guaranteed Access: Every item in a table must be logically addressable with the help of a table name.
  • The Systematic Treatment of Null Values: The RDBMS must be taken care of null values to represent missing or inapplicable information.
  • The Database Description Rule: A description of database is maintained using the same logical structures with which data was defined by the RDBMS.
  • Comprehensive Data Sub Language: According to the rule the system must support data definition, view definition, data manipulation, integrity constraints, and authorization and transaction management operations.
  • The View Updating Rule: All views that are theoretically updateable are also updateable by the system.
  • The Insert and Update Rule: This rule indicates that all the data manipulation commands must be operational on sets of rows having a relation rather than on a single row.
  • The Physical Independence Rule: Application programs must remain unimpaired when any changes are made in storage representation or access methods.
  • The Logical Data Independence Rule: The changes that are made should not affect the user’s ability to work with the data. The change can be splitting table into many more tables.
  • The Integrity Independence Rule: The integrity constraints should store in the system catalog or in the database.
  • The Distribution Rule: The system must be access or manipulate the data that is distributed in other systems.
  • The Non-subversion Rule: If a RDBMS supports a lower level language then it should not bypass any integrity constraints defined in the higher level.

Object Relational Database Management System

Oracle8 and later versions are supported object-oriented concepts. A structure once created can be reused is the fundamental of the OOP’s concept. So we can say Oracle8 is supported Object Relational model, Object – oriented model both.

Oracle products are based on a concept known as a client-server technology. This concept involves segregating the processing of an application between two systems. One performs all activities related to the database (server) and the other performs activities that help the user to interact with the application (client). A client or front-end database application also interacts with the database by requesting and receiving information from database server. It acts as an interface between the user and the database. The database server or back end is used to manage the database tables and also respond to client requests.

Client/Server Overview

  • Client/Server architecture splits an application into tasks that are executed as separate processes
  • Client/Server architecture is designed to assign tasks to the most appropriate processor
  • Diverse areas of IT are involved, such as
    • User Interface
    • Database Programming
    • Networking
    • Distributed Data and Distributed Processing

Definition of Client/Server Computing

In Client/Server computing the application and data are distributed over Client System(s) sending requests and Server System(s) serving the request over a network.

The Client (often referred as the front-end) in a Client/Server model is a(ny) hardware platform, which handles the functionality of user interface, user request and user presentation. It may also have some local data and local processing.

The Server in a Client/Server model (the back-end) is a(ny) hardware platform, which handles requests and interface to a database.

Key Benefits of Client/Server Architecture

  • Empowering Users :
    • User driven applications
    • Better User interface and utilization of resources
    • Intelligent workstations provide good interaction with the users
  • Interoperability:
    • High-power, inexpensive servers provide data repository and processing functions.
    • Can be designed to offer open architecture (open connectivity and protocol)
  • Extensibility:
    • Modular processor can be sized to match requirements
    • Advantage of latest technology
  • Cost Advantages:
    • Increased productivity due to better technological response
    • Less operational cost of Client/Server system
    • High processing power of Client work-stations
    • Wider range of open and economic products
    • Better location of data
    • Better mapping of data

Client/Server solutions are based on distributed data and processing. As a result, the data resides where it logically belongs. Each Client owns its local data and has a secured access to a central database.

As desktops are becoming powerful and plenty, it makes economic sense to distribute the Client functionality on cheaper desktops. As a direct consequence, it frees some of the costly Server capability. Latest techniques support Client/Server computing such as Rapid Application Development, Information Modeling and GUI. These tools and techniques increase programmer and user productivity. The ability to add servers to meet performance and geographical demand, without having to redesign the whole system, is another major advantage of a Client/Server system.

Distributed Processing in Client/Server

  • Presentation Logic : User Interface, Client Application Logic
  • Application Logic : Business rules
  • Database Logic
  • RDBMS

 oracle5

When major application components are distributed, the link between them must be transparent, with well-defined boundaries and protocols.

The Role of an Application Program Interface (API) is to ensure a formal, standard and clean interface between the application components.

  • Manage Windows
  • Manage dialogues
  • Do local processing
  • Manage presentations
  • Interface with utilities
  • Apply external controls
  • Interface with Server(s)

The Client and Server’s Role in Distributed Processing

oracle6

 

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One Response to “Overview of Oracle – Part I”

  1. Kym Herber said

    Valuable info. Fortunate me I discovered your web site unintentionally, and I’m shocked why this coincidence didn’t came about in advance! I bookmarked it.

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