Now that we have finished with the evolution of databases and the uses of a DB,the next important portion is understanding the architecture of a database system.A Db is complex piece of software that usually consists of a number of modules.As we know the PRIME aim of a DB is to handle data efficiently for the wide array of users,the DB must be aware of the data it is holding,or simply to help users, DB must maintain ” information about the DATA ” itself.This information include what data is stored,how it is stored,who can access to what parts of it etc.This information(DATA)about the data in a database is called the METADATA.

Users of a Database:A DB has three broad class of users-

1. Application Programmers.
2. End Users.
3. Database Administrator(DBA)#.

Application programmers are those people writing programs that use the database.End users are people who interact with the DB using an application or some interfaces,they usually dont know even about the existence of such software called database.DBA is the person who administers the DB.He creates the actual DB and implements the technical controls,maintains data security etc.

Components of A Database

1. Query Language:-is a programming language which is english like and more understandable,which helps the users to store and retrieve data.
2. Query Processor:-Translates statements in a query language into low level instructions that the DB understands.
3. Database Manager:- acts as an interface between applications programs,low level data and queries submited by users.
4. File Manager:-manages the disk space,storage and diferent data structures used to represent information on disk.

One basic characteristic of this database approach is that it provides a level of data abstraction by hiding certain details from users,which means each user will see only those data which they are expected to see.A DATA MODEL helps the DB in doing this.There are THREE categories of data models

1. Conceptual.
2. Physical.
3. Representational.

The goal of three schema architecture is to seperate the users from the physical database.The internal level is the one closest to physical storage,external is the one closest to the users,it is concerne about how data is viewed by diferent users.The conceptual level is an intermediate level between the other two levels.

A term while talking about databases that we come across is SCHEMA.What is a SCHEMA??Very precisely it is a description of data in terms of a data model.And the description of a database is called database SCHEMA.Now we are slowly moving to Database Models,

1. Relational Model:-Here every item in the DB is viewed as a record with certain attributes.And records with similar attributes is called a table.Eg: for DBMS’ which use relational model are Oracle,MySQL,Sybase etc.
2. Network Model:-This also considers data as records but difference from reational model is that each record will have a link field which will link to other records.Eg:-IDS(Integrated Data Store).
3. Hierarchical Model:-Here data is represented in hierarchical format as in a tree.This is a special type of network model,where a parent can have many children.

With this i am concluding on the initial requirements for studying a particular Relational Database Management System.From next chapter onwards we will give more stress to a particular DB,mostly Oracle or MS SQL Server.

#Functions of a DBA:

• Defining conceptual models and schema.
• Physical database design and mapping between internal and conceptual schemas.
• Defining security and integrity  rules.
• Defining backup and recovery mechanisms.
• Monitoring performance.

Related posts:

1. RDBMS Chapter-3
2. RDBMS basics
3. C Language – Fundamentals
4. Constants and Variables
5. Arrays