How oracle databases work?


Oracle consists of a complete set of applications and product manufacturers to users, seeking to provide information technology solutions. Oracle applications are portable across a large number of workstations and operating systems, from PCs to parallel processors. Oracle is equipped with a flexible Database Management System (DBMS), Oracle Server, used for storage and information management applications. Last Oracle Server, Oracle 7, run a database with all the advantages of relational structures, with extra capacity to store and execute database objects such as safety procedures and mechanisms.

About Oracle Server

Oracle DBMS which includes a control:
Storing data in the field of databases dedicated; Data recovery applications using appropriate optimization techniques; Database Security Tasks and allowed for some users; Consistency and data protection, including archiving tasks and search mechanisms; Communication and integrity of information when databases are distributed across a network.

Oracle applications must run on the same computer as server and Oracle. Alternatively, applications and tools used by them can be run on a local system user (system ‘customer’), while Oracle DBMS running on another system (‘server’).

In this environment ‘client server’, many computing resources can be run. As an example, an application ‘Oracle Forms’ can run on a personal computer client while accessing data is conventionally managed by the Oracle Server a central computer.

Oracle Server Features
In addition to ‘standard Oracle7′ which has many facilities on comprehensive databases, there are several additional features.

These include:

Procedural option
Provide an “engine” PL / SQL version 2 server inside Oracle, which has the ability to store procedures Blvd, safety features and mechanisms for use by applications.

Distributed Option
Supports transactions that updated information from multiple databases in a network of distributed databases using executed in two phases.

Parallel Server Option
Coupled open systems support. Oracle trust (“Trusted Oracle”). Provides plenty of additional high-security facilities.

Oracle products
Among the many application development and user products available in the Oracle family, there is a possibility to access the common database: the Structure Query Language (SQL).

Oracle products contain:

Oracle Text Retrieval
A technology that adds capabilities for complete restoration of the text in an Oracle database.

Oracle Pro *
A number of precomilator allowing access to Oracle database programming languages C, Cobol, Fortran, PL / 1, Pascal and Ada.

Oracle Card
A user interface for production applications with user friendly databases to incorporate graphics and multimedia features.

Oracle CASE
A family of tools that help analyze, design and generation of Oracle applications.

SQL * Plus
A tool that allows a direct and interactive use of language to access Oracle database using ad hoc commands or by running the command file.

Ancillary development environment (CDE).
Main application development tool set forms a closed integrated called ‘Subsidiary Development Environment. “CDE include basic elements of Oracle’s procedural language, PL / SQL, graphics and communication facilities between products.

CDE main tools are:

Oracle Forms V4
Allow sophisticated applications to be built using the screen quickly and easily and allows the user to request and manipulate data in convenient shape structure, as well as displaying visual images, and access facilities provided by other CDE.

Oracle Reports V2
A powerful report writing tool for building and executing sophisticated reports with multiple images and text fonts.

Oracle Graphics v2
To build and display video applications, including maps, graphs, pictures and drawings.

Oracle Book V1
Provides the ability to create and view documents include hypertext, digital audio, and video.

SQL and SQL * Plus PL / SQL

SQL, SQL * Plus and PL / SQL is Oracle’s facilities which will be discussed in this curs. It is important to understand the differences in each case their role and their place in the Oracle family.


is the language used to access a relational database, including Oracle.

each instrument can be used Oracle database when access is necessary.

* PL / SQL

is Oracle’s procedural language for writing applications for handling data outside the database.

may include a subset of SQL when database access is required

is available in each of the products also in itself CDE.De Oracle (if procedural option is installed).

* SQL * Plus

Oracle is a product which languages SQL and PL / SQL can be used. Language also has its own command and control product behavior for formatting SQL query results.

In conclusion, SQL and PL / SQL are languages that are used in a number of Oracle products. SQL * Plus is one of the products on which they are located.

We will now discuss the basic principles of relational databases, where Oracle is an example.

Relational approach

Principles of relational model were first exposed by Dr. EFCodd, which in June 1970 published an article called ‘A relational model of data for large data banks “. In this article, Dr. Codd proposed the model of’ relational ‘for database systems.

Relational database is perceived by its users as a collection of two-dimensional tables that are easily understood inteles. There are only four concepts:





Relational model mimics a branch of algebra processes known as the ‘relational algebra. “These processes involve:

a collection of objects known RELATIONS

a lot of what operators that activates on relations to produce new relationships.

A relationship can be understood as a Table. Data modification is realized by relational operations applied to tables.

Relational Operators

Relational operators are defined below:

Relationship / description

Is an operation that retrieves and displays data from the relation. It is possible to display all rows or only rows that meet a condition or several conditions. This is often called ‘subset horizontal’

Is the operation that displays some columns that relationship and is called ‘vertical subset’.

Is the result when the two sets of data lines are concatenated according to specified conditions.

Is the result when the two sets of data lines are concatenated according to specified conditions.

Displays all rows that appear in one, the other or both of the two relationships.

Displays all rows that appear in both of the two relationships.

Displays lines that appear only in one relationship (database operator uses less).

Properties of relational databases.
A relational database is a collection of relations (tables) to the user.

The format of the column / row is familiar and easy to visualize data.

There are plenty of operators for partitioning and combining relations (selection, projection, product, join, union, intersection, difference).

There are no explicit pointers; connections are made only on the data.

The language used to query the database and is non-procedural language like English.

The user does not specify the path and does not need to know how information is physically arranged.

Commands for data recovery and to achieve those changes in the database are included in a single language database.

There is a totally independent data.

Tabular relations properties.

One table has the following features:

No duplicate rows.

There are duplicate column names.

Order of rows is unimportant.

Columns order is unimportant.