CS403 Short Notes Set 3 by VUBuddy

Database definitions:

A shared collection of logically related data, designed to meet the information needs of multiple users in an organization.

o Database Application:

Database Application is a program or group of programs which is used for performing certain operations on the data stored in the database. These operations may contain insertion of data into a database or extracting some data from the database based on a certain condition, updating data in the database, producing the data as output on any device such as Screen, disk or printer.

o Database Management Systems:

Database management system is software of collection of small programs to perform certain operation on data and manage the data. Two basic operations performed by the DBMS are:

 Management of Data in the Database

 Management of Users associated with the database.

Further Advantages of Database Systems:

Database systems are very much beneficent to enterprises and businesses, some of the advantages are listed below: o Data consistency o Better data security o Faster development of new applications o Economy of scale o Better concurrency control o Better backup and recovery procedures

o Data Consistency:

Data consistency means that the changes made to different occurrence of data should be controlled and managed in such a way that all the occurrences have same value for any specific data item

Better Data Security:

All application programs access data through DBMS, So DBMS can very efficiently check that which user is performing which action and accessing which part of data , So A DBMS is the most effectively control and maintain security of Data stored in a database.

o Economy of Scale:

Databases and database systems are designed to share data stored in one location for many different purposes, So it needs not be stored as many number of times in different forms as it is used, for example the data used by Admission Department of any education institution can be used to maintain the attendance record of the students as well as the examination records of the students. So it saves us lots of efforts and finances providing

o Better Concurrency Control:

Concurrency means the access of database form as number of points simultaneously. Concurrency control means to access the database in such a way that all the data accesses are completed correctly and transparently. One example of controlled concurrency is the use of ATM Machine for withdrawal of money (cash). All ATM machines of a bank are interconnected to a central database system worldwide, so that a user can access its account from anywhere in the world and can get cash from any ATM terminal. As there are thousands of ATM terminal across the world for a specific bank so as a result thousands of user process and access the bank’s database. All this process is managed concurrently using the database systems and is done in such an efficient manner that no two user face any delay in the processing of their requests.

Better Backup and Recovery Facility:

Data is a very important resource and is very much valuable for any organization, loss of such a valuable resource can result in a huge strategic disasters. As Data is stored on today’s’ storage devices like hard disks etc., It is necessary to take periodic backups of data so that in case a storage device looses the data due to any damage we should be ableto restore the data a nearest point, Database systems offer excellent facilities for taking backup of data and good mechanism of restoring those backups to get back the backed-up data.

o High Cost:

Database Systems have a number of inherent charges which are to be born by any organization that is going to adopt it. High Cost is one of these inherent charges, it includes the need for specialized software which is used to run database systems, Additional and specialized hardware and technically qualified staff are the requirements for adopting to the database system, all these requirements need an organization to invest handsome amount of money to have all the requirements of the database systems.

o Conversion Cost:

Once an organization has decided to adopt database system for its operations, it is not only the finance and technical man-power which is required for switching on to database system, it further has some conversion charges needed for adopting the database system,

o Difficult Recovery Procedures:

Although the database systems and database management systems provide very efficient ways of data recovery in case of any disaster, still the process of recovering a crashed database is very much technical and needs good professional skills to perform a perfect recovery of the database.

Importance of Data

o Data as a Resource:

A resource is anything which is valuable for an organization. There can be a number of resources in any organization, for example, Buildings, Furniture, Vehicle, Technical Staff, Managers, supporting staff and Machinery etc. As all these are resources for organizations and are consumed very much carefully to get full benefit out of them.

Data

in the same way is a very important resource and needs to considered equally important as other resource are considered.

Levels of Data

o Real World Data

The real world level of data means that level of data at which entities or objects exist in reality, it means that any object existing in reality have a name and other identifiable attributes through which we can identify that specific object or entity.

Example:

Any Student o Meta Data: For storage of the data related to any entity or object existing at real world level we define the way the data will be stored in the database. This is called Meta data. Meta data is also known as schema for the real world data. Example: Name , Character Type, 25 character size field, Age, Date type, 8 bytes size Class, Alpha Numeric, 8 byte size field

o Existence of Data:

Existence of the data level shows the actual data regarding the entities as real world level according to the rules define at the Meta Data level.

Example:

According to the definition given in the Meta data level the Actual data or Data occurance for the entity at real world level is shown below: Name Age Class Ali 20/8/1979 MCS-I Amir 22/3/1978 MCS-II etc…

Users of Database Systems: · o Application Programmers · o End Users ·  Naïve ·  Sophisticated ·  Naïve Users

This category of users is that category who simply use the application database programs created by the programmers. This group has no interaction with other parts of there database and only use the programs meant for them. They have not to worry about the further working of the database.

 Sophisticated Users:

This type of users has some additional rights over the Naïve users, which means that they can access the data stored in the database any of their desired way. They can access data using the application programs as well as other ways of accessing data.

o Database Administrators (DBA):

This class of database users is the most technical class of db users. They need to have the knowledge of how to design and manage the database use as well as to manage the data in the database. DBA is a very responsible position in an organization. He is responsible for proper working of the database and DBMS, has the responsibility of making proper database backups and make necessary actions for recovering the database in case of a database crash.

 Duties of the DBA · o Schema definition · o Granting data access · o Routine Maintenance ·  Backups ·  Monitoring disk space ·  Monitoring jobs running