Wednesday, April 21, 2010

Introduction to Oracle DataBase

ORACLE is a fourth generation relational database management system. In general, a database management system (DBMS) must be able to reliably manage a large amount of data in a multi-user environment so that many users can concurrently access the same data. All this must be accomplished while delivering high performance to the users of the database. A DBMS must also be secure from unauthorized access and provide efficient solutions for failure recovery. The ORACLE Server provides efficient and effective solutions for the major database features.

ORACLE consists of many tools that allow you to create an application with ease and flexibility. You must determine how to implement your requirements using the features available in ORACLE, along with its tools. The features and tools that you choose to use to implement your application can significantly affect the performance of your application.

Several of the more useful features available to ORACLE application developers are integrity constraints, stored procedures and packages, database triggers, cost-based optimizer, shared SQL, locking and sequences.

An Oracle database is a collection of data treated as a unit. The purpose of a database is to store and retrieve related information. A database server is the key to solving the problems of information management. In general, a server reliably manages a large amount of data in a multiuser environment so that many users can concurrently access the same data. All this is accomplished while delivering high performance. A database server also prevents unauthorized access and provides efficient solutions for failure recovery.

Oracle Database is the first database designed for enterprise grid computing, the most flexible and cost effective way to manage information and applications. Enterprise grid computing creates large pools of industry-standard, modular storage and servers. With this architecture, each new system can be rapidly provisioned from the pool of components. There is no need for peak workloads, because capacity can be easily added or reallocated from the resource pools as needed.

The database has logical structures and physical structures. Because the physical and logical structures are separate, the physical storage of data can be managed without affecting the access to logical storage structures.

Advantages of Oracle DataBase

Oracle takes a lead role because of some of the following reasons:

Oracle is used for almost all large application and one of the main applications in which oracle takes its major presence is banking. In fact ten of the world’s top 10 banks run Oracle applications this is because oracle offers a powerful combination of technology and comprehensive, pre-integrated business applications, including key functionality built specifically for banks.

Oracle is a database that responds very well with excellent performance in demanding environments. Oracle is a major database which along with its added features passes the ACID test, which is important in insuring the integrity of data. This is very important because data is the heart of any system in organization. A reliable and adequate database system has the following properties:

Atomicity:

That is Results of a transaction's execution are either all committed or all rolled back.

Consistency:

The database is transformed from one valid state to another valid state. Illegal transactions aren't allowed and, if an integrity constraint can't be satisfied then the transaction is rolled back.

Isolation:

The results of a transaction are invisible to other transactions until the transaction is complete thus increasing the security on data.

Durability:

Once committed (completed), the results of a transaction are permanent and survive future system and media failures and thus ensuring maintenance and protection of data.

All the above are well maintained by Oracle database.

The latest version oracle 10g has many features and one new feature is the introduction of recycle bin. This option when enabled could be used by users just like Windows recycle bin or Mac Trash. Dropped tables go "into" the recycle bin, and can be restored from the recycle bin.

Built-In Packages

A package is an encapsulated collection of related program objects stored together in the database. Program objects are procedures, functions, variables, constants, cursors, and exceptions.

The following packages are especially useful in application development for Oracle Database:

DBMS_PIPE is used to communicate between sessions.

DBMS_ALERT is used to broadcast alerts to users.

DBMS_LOCK and DBMS_TRANSACTION are used for lock and transaction management.

DBMS_AQ is used for Advanced Queuing.

DBMS_LOB is used to manipulate large objects.

DBMS_ROWID is used for employing ROWID values.

UTL_RAW is the RAW facility.

UTL_REF is for work with REF values.

The following packages are useful for server manageability:

DBMS_SESSION is for session management by DBAs.

DBMS_SPACE and DBMS_SHARED_POOL provide space information and reserve shared pool resources.

DBMS_JOB is used to schedule jobs in the server.