Dbms (Obms & Oracle 91)

Topics: Database, Data modeling, Database management system Pages: 15 (4599 words) Published: July 12, 2013
MC0067 - 01
Marks - 40 DBMS (OBMS & ORACLE 91)

1.Write a note on File based system/ Data base system


File-Based Systems:
Conventionally, Before the database Systems evolved , data in the software’s Systems was stored in and represented using flats files.

Drawbacks of File-Based Systems:

File - Based Systems


As shown in the figure, in a file-based system, different programs in the same application may be interacting with different private data files. There is no system enforcing any standardized control on the organization and structure of these data files. •Data Redundancy and Inconsistency

Since data resides in different private data files, there are chances of redundancy and resulting inconsistency. For example, in the above example shown, the same customer can have a savings account as well as a mortgage loan. Here the customer details may be duplicated since the programs for the two functions store their corresponding data in two different data files. This gives rr.>e to redundancy in the customer's data. Since the same data is stored in two files, inconsistency arises if a change made in the data in one file is not reflected in the other. •Unanticipated Queries

In a file-based system, handling sudden/ad-hoc queries can be difficult, since it requires changes in the existing programs. •Data Isolation
Though data used by different programs in the application may be related, they reside in isolated data files. •Concurrent Access Anomalies
In large multi-user systems the same file or record may need to be accessed by multiple users simultaneously. Handling this in file-based systems is difficult. •Security Problems
In data-intensive applications, security of data is a major concern. Users should be given access only to required data and not the whole database. In a file-based system, this can be handled only by additional programming in each application.

2. What are the Roles and responsibilities of database administrator?


The role of a DBA is very important and defined by the following functions. • Defining the schema
The DBA defined the schema which contains the structures of the data in the application.

Liaising with Users
The DBA needs to interact continuously with the users to understand the data in the system and its use.

Defining Security & Integrity Checks
The DBA finds about the access restrictions to be defined and defines security checks accordingly. Data Integrity checks are also defined by the DBA.

Defining Backup I Recovery Procedures
The DBA also defines procedures for backup and recovery. Defining backup procedures includes specifying what data is to backed up, the periodicity of taking backups and also the medium and storage place for the backup data.

• Monitoring Performance
The DBA has to continuously monitor the performance of the queries and take measures to optimize all the queries in the application

3. Define the following terms
(i) Database
(ii) Database Management System
(iii) Data Model
(iv) Scheme
(v) Data independence
A Database is a collection of interrelated data and a Database Management system is a set of programs to use and/or modify this data. Due to its centralized nature the database system can overcome the disadvantages of the file based system as discussed below: • Minimal Data Redundancy

Since the whole data resides in one central database, the various programs in the application can access data in different data files. And data need not to be duplicated. • Data Consistency

Reduced data redundancy leads better data consistency.
As we can see that a Database offers various features over file based system. Database Management System:
A Database is a collection of interrelated data and a Database Management system is a set of programs to use...
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