Oracle 9i Database Administration in 10 Minutes

- Asim Abbasi (Author)

Chapter 1: Understanding the Oracle Environment

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Oracle is such a complex system that without analogies it’s very hard to comprehend and grasp the concept of Oracle architecture and it’s working. Also once you understand the concepts then there is nothing left for cramming.

Oracle System is basically divided into two things namely Oracle Instance and Oracle Database. We have taken the analogy of a Genie (Ghost/Djin): just like the one you might have seen in the movie/story of “Aladdin & the Magic Lamp”. When Aladdin rubbed the lamp; Genie became available and fulfilled all his commands. Similarly when you double click “Oracle” icon in your system, Oracle Instance gets alive and waits for users information/data related commands to fulfill, as it is a magnificent “Data Management Genie”.

Oracle Instance is something with which users interact in terms of storing and retrieving information. Anything that is going into the database or coming out of the database has to be through Oracle Instance and to communicate with Oracle Instance we need to learn Genie’s language: SQL. It stands for Structured Query Language and pronounced as See-Qual.

The Oracle Database is basically Genie’s area to write information and to make the changes permanent on the hard disk. The communication between Oracle and user takes place in a fashion that first user has to establish a connection with Oracle server or more precisely oracle instance by providing his/her credentials (Username and password). Once verified, Oracle accepts the connection otherwise the connection request will get rejected.

Figure 1: The Complete Oracle System: Oracle Instance & Oracle Database.
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Chapter 1: Understanding the Oracle Environment

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Oracle 9i Database Administration in 10 Minutes