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CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
APR2016
ASSESSMENT_CODE BT0066_APR2016
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73047
QUESTION_TEXT
Explain data base manager, database administrator & data dictionary
SCHEME OF
EVALUATION
Database Manager: The program module called Database manager is the
one which provides interface between row data stored in the database
and application programs. The queries are submitted to the system
through the application. One of the main responsibilities of database
manager is to provide interface with file system…
Database Administrator: A major reason for a database management
system is to have control over data and programs access to these data.
Such people we call database administrator (DBA)…
Data Dictionary
It is extremely difficult to keep track of all available names and also the
purpose of using these names, as size of the program increases in larger.
Only the programmer can keep in mind regarding the available names.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73048
QUESTION_TEXT
Explain magnetic disks along with its physical characteristics,
performance measures & optimization of disc block access.
Magnetic Disks
SCHEME OF
EVALUATION
The magnetic disks facilitate the bulk of secondary storage. In the
modern computer systems the storage capacity requirements have been
growing at over 50 percent per year.
Physical Characteristics of Disks
Each disk platter has a flat circular shape. Its two surfaces are covered
with a magnetic material, and information is recorded on the surfaces.
Platters are made from rigid metal or glass and are covered (usually on
both sides) with magnetic recording material. The disk surface is
logically divided into tracks, which are subdivided into sectors. A
sector is the smallest unit of information that can be read from or written
to the disk.
Performance Measures of Disks
The quality of a disk can be measured by its access time, capacity,
reliability and data-transfer-rate.
Access time is the time from when a read or write request is issued to
when data transfer begins.
4 Optimization of Disk-Block Access
In most of the operating system the disk I/O request generated by file
system and by virtual memory manager. Here the request provides
address on the disk and this address is in the form of a block number. A
block is a contiguous sequence of sectors from a single track of one
platter.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73049
QUESTION_TEXT
Explain E.R model.
SCHEME OF
EVALUATION
The Entity-Relationship Model
In conceptual schema we make use of tool called entity-relationship
model to represent and analyze the features of an application. Entityrelationship model approach includes a graphical notation, where entity
represent as rectangle shape, relationship as diamond shape, and
attributes as oval or circle shape…
This is the best tool for transition from an information application
description to a formal database schema. In an enterprise entityrelationship model is used for describing the conceptual schema. The
description of physical schema not defined at this stage. The entityrelationship diagram is then used to design logical schema in which the
database is actually implemented…
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118248
QUESTION_TEXT
What are the alternative object oriented database strategies? Explain
them
-
Novel database data model
Extending an existing database language with objectorientation capabilities
SCHEME OF
EVALUATION
Extending an existing object-oriented programming language
with database capabilities
Embedding object-oriented database language constructs in a
host language
All 4 to be explained & each carries 2.5 marks
QUESTION_T
DESCRIPTIVE_QUESTION
YPE
QUESTION_ID 163210
QUESTION_T
Explain the anomalies in a database.
EXT
Anomalies in a Database
Let us consider a relation schema regarding the information about an
employee of an organization.
SCHEME OF
EVALUATION EMP_PROJ(Ssn, Pnumber, Hours, Ename, Pname,Plocation)
Tuples of a relation on the relation schema EMP_PROJ(Ssn, Pnumber, Hours,
Ename, Pname, Plocation) are shown in Table 9.2. Figure 9.3 shows the
functional dependencies among its attributes. The key attributes of the
relation are Ssn, Pnumber. Function dependencies of the relation { Ssn,
Pnumber Hours, Ssn  Ename, Pnumber  Pname, Plocation}
Table 9.2: Employee Data Representation in Relation EMP_PROJ
Attribute Ename is not functionally dependent on the whole key, but partially
depend on the one of the key namely Ssn. Similarly Pname and plocation
partially depends on attribute Pnumber. Only the attribute Hours is fully
functionally dependent on the key Ssn, Pnumber.
There are several undesirable problems in relation schema EMP_PROJ.
Redundancy: The objective of the database system is to reduce duplicate data being
stored in database, which in turn leads to waste of storage space, increases the size
of the data stored and also some time leads to inconsistencies among the data.
Whenever an update operation conducted on a database with high
redundancies this leads to inconsistent state which are explained below. Table
9.2 contain attributes Pname and Plocation of project are stored several times
where one of employee and another for project.
Update Anomalies: Update anomalies are occurs when multiple copies of same fact
exist in the database. This also leads to inconsistencies, when only some of many
copies are updated. Consider relation schema Figure 9.3 a change in the Plocation
of project number 2 made consistent in all the tuples related to project number 2. If
the update is not reflected one of the three tuples then there will be an
inconsistency in the data.
Insertion Anomalies: In the given relation schema we cannot enter only
project name & location for a given project number and this not meant for .
We need to have employee with proper SSN to him.
Deletion Anomalies: Given the project an individual employee wants to
discontinue, there is always possibility that we may lose information
regarding project name and its location. And this could happen if we maintain
single relation which maintains all these information in it. If we have another
relation for project information then deletion of any tuple from EMP_PROJ
will not cause any information lost.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
163211
QUESTION_TEXT
When BCNF is needed? Explain BCNF.
Boyce-Codd Normal Form (BCNF)
Consider a composite key attribute in a relation which having common
attribute. If there exist any dependency among the attribute of composite
key then that relation require a normalization called BCNF. Let us
consider an example, the relation Employee:
Employee (Employee code, Project, Project head, Percent time)
SCHEME OF
EVALUATION
Let us assume that
1.
An employee can work more than one project
2.
Percentage of hours he/she works for each project is given.
3.
Each project monitored by project head.
…………………………………………..