Short Notes on DBMS

1. DATABASE MANAGEMENT SYSTEM:
UNIT - 1
1. Define dbms?
Database management system is a collection of interrelated data and set of
programs to access those data.
2. Application of dbms?
 Banking
 Airlines
 Universities
 Credit card transactions
 Telecommunication
 Finance
 Sales
 Manufacturing products
 Human resources
3. Define integrity?
The data values stored in the database must satisfy certain types of consistency
constraints
4. Define isolation?
The data are scattered in various files and files maybe in different formats, writing
new application programs to retrieve the appropriate data is difficult.
5. Define data abstraction?
The system hides certain details of how the data are stored and maintained, this is
called data abstraction.
6. Give the levels of abstraction?
 Physical level
 Logical level
 View level
7. Define instances and schemas?
Instances: The collection of information stored in the database at a particular moment is
called an instance of a database.
Schema: The overall design of the database is called the database schema.

2. 8. Define data model?
A collection of conceptual tool for describing data, data relationships, data
semantics and consistency constraints.
9. Define ER model?
The entity relationship data model is based on a perception of a real world that
consists of a collection of basis objects called entities and of relationships among these
objects.
10. Define attribute?
Attributes are descriptive properties possessed by each member of an entity set
11. Define relationship?
A relationship is an association among several entities.
12. Define DML?
A data manipulation language that enables user to access or manipulate data as
organized by the appropriate data model.
13. Define DDL?
A database schema by a set of definition expressed by a special language called a
Data Definition Language
14. Define DDL interpreter?
DDL interpreter which interprets DDL statements and records the definitions in
the data dictionary
15. Define data dictionary?
Data dictionary which stores meta data about the structure of the database, in particular
the schema of the database.
16. What is meant by single & multi valued attributes?
Single valued attributes:
The attributes which have a single value for a particular entity, such attributes are
said to be single valued attributes
.Multi valued attributes:

3. The attributes which have a set of values for a particular entity, such attributes are
said to be multi valued attributes
17. Define relationship set?
A relationship set is a set of relationships of the same type.
18. What is meant by mapping cardinalities?
Mapping cardinalities express the number of entities to which another entity can
be associated via a relationship set.
19. Diffrentiate total & partial participation?
Total participation:
The participation of an entity set E in a relationship set R is said to be total if
every entity in E participates at least in one relationship in R.
Partial participation:
If only some entities in E participates in relationship in R, the participation of the
entity set E in relationship R is said to be partial.
20. Define key?
A key allows us to identify a set of attributes that suffice to distinguish entities
from each other. Keys also help uniquely identify relationships and thus distinguish
relationships from each others.
21. Define super, candidate, primary, foreign keys?
Super key:
A super key is a set of one or more attributes that taken collectively, allow us to
identify an entity uniquely in the entity set.
Candidate key:
A super key which does not have a subset is called a candidate key.
Primary key:
The term primary key to denote a candidate key that is chosen by the database
designer as the principal means of identifying entities within an entity set.
Foreign key:

4. A relation schema r1 derived from an E-R schema may include among its
attributes of the primary key of another relation schema r2. this attribute is called foreign
key from r1, referencing r2
22. State the major components of ER diagram?
 Rectangles-represents entity set
 Ellipses-represents attributes
 Diamonds-represent relationship sets
 Lines-links attributes to entity sets and entity sets to relationship sets
 Double ellipses-represents multi valued attributes
 Dashed ellipses-represents derived attributes
 Double lines-represents total participation of an entiy in a relationship set
 Double rectangles-represents weak entity set
23. Define weak entity set?
An entity set may not have sufficient attributes to form a primary key. Such an
entity set is termed as weak entity set.
24. Define strong entity set?
An entity set that has a primary key is termed as strong entity set.
25. What is meant by aggregation?
Aggregation is an abstraction through which relationships are treated as higher
level entities. Can also participate in relationships
26. What is meant by UML?
The Unified Modelling language provides a graphical means of modeling various
components of a software system.
27. Give the parts of UML?
 Class diagram: A class diagram is similar to an ER diagram
 Use case diagram: use case diagrams show the interaction between the users
and the system in particular the steps of task for that users perform
 Activity diagram: Activity diagrams depict the flow of task between various
components of the system.
 Implementation diagram: implementation diagram shows the system
components and their interconnections, both at the software component
level and the hardware component level
28. What is a DML complier?

5. DML complier which translates DML statements in a query language into an
evaluation plan consisting of low level instructions that the query evaluation engine
understands.
29. what is two-tier architecture?
The application is partitioned into a component that resides at the client machine,
which invokes a database system functionality at the server machine through query
language statements.
30. what is three-tier architecture?
The client machine act as merely a front end and does not contain any direct
database calls. Instead, the client end communicates with an application server, usually
through a form interface. The application server in turn communicates with a database
system to access data.
UNIT II
1. What is a query language?
The query language is the language in which a user request information from the
database .These languages are usually on a level higher then that of a standard
programming language .
2. What in procedural and non procedural languages?
In procedural languages ,the user instructs the system to perform a sequence of
operation on the database to compute the desired result.
In nonprocedural language, the user describes the desired information without
giving a specific procedure for obtaining that information.
3. What in Cartesian –product operation?
The Cartesian –product operation denoted by a cross(X),allows us to combine
information from any two relations. we write the Cartesian product of relations r1 and r2
as r1 x r2.
4. Define domain?
For each attribute, there is a set of permitted values called the domain. For the
attribute branch name, for example, the domain is the set of all branches name.
5. Define relation?

6. Relation to be a subset of a Cartesian product of a list of domains.
6. Define tuples?
A tuple variable is a variable that stands for a tuple,in other words a tuple variable
is a variable whose domain is the set of all tuples.
7. What is the relation schema?
The concept of a relation schema corresponds to the programming –language
notion of type definition. We use Account –schema to denote the relation schema for
relation account.
Account-schema = (account-number ,branch-name ,balance)
We denote the fact that account is a relation on Account –schema by
Account (Account-schema)
8. What is database schema?
Database schema in the logical design of the database.
9. What is database instance?
Database instance is a snapshot of the data in the database at a given
instant in time.
10. What is relation instance?
The concept of a relation instance corresponds to the programming
language notion of a value of a variable.
11. What is relational algebra?
The relational algebra is a procedural query language .It consists of set of
operations that take one or two relations as input and produce a new relation as their
result. The fundamental operation in the relational algebra is select, project, union, set
difference, Cartesian product and rename.
12. What is select operation?
The select operation selects tuples that satisfy a given predicate .we use
the lower case Greek letter sigma (σ).to denote selection. The predicate appears as a
subscript to σ .The argument relation in parentheses after the σ
13. Describe extended relational operation?

7. The basic relation –algebra operation have been extended in several ways.
The simple extension is to allow arithmetic operations as part of projection. An important
extension is to allow aggregate operations such as computing the sum of the elements of
a set. Or their average.
14. What is meant by aggregate function?
Aggregate function takes a collection of values and return a single value as a
result.
15. What is meant by multiset?
The collections on which aggregate functions operates can have multiple
Occurrences of value ;the order in which the value appear in not relevant .such
collections are called as multisets.
16. What is outer join?
Outer join operation is an extension of the join operation to deal with missing
information . suppose that we have the relations with the following schemas ,which
contains data on full-time table name.
17. What are the types of outer join?
 left outer join
 right outer join
 full outer join
18. What is meant by null values?
The special values are called as Null values indicates “value
unknown or non existent” ,any arithmetic operation such as(+,-,*,/) involving null values
must return a null result
19. In SQL operation how the different relational operation deal with null values ?
 select
 join
 projection
 union, intersection, difference
 generalized projection
 aggregate
 outer join
20. Define modification of database?

8. It contains following operations like
 deletion
 insertion
 update
21. Define view?
We define a view by using the create view statement .To defene a view, we
must give the view a name ,and must state the query the computes the view. The form of
create view statement is Create view v as <query expression>
22. What is meant by tuple relation calculus?
The tuple relation calculus, by contrast is a, non procedural query language .It describes
the desired information without giving the specific procedure for obtaining that
information. A query in the tuple relational calculus is expressed as {t|P(t)}
23. What is meant by domain relation calculus?
A second form of relational calculus are called domain relational calculus.
24. What are the parts of SQL languages?
There are several parts in SQL language
 data-definition language(DDL)
 interactive data manipulation language(DML)
 view definition
 transaction control
 embedded SQL and dynamic SQL
 integrity
 authorization
25. Explain the basic structure SQL?
The basic structure of an SQL expression consist of three clauses;
Select from where
26. Define select ?
The select clauses corresponds to the projection operation of the relational
algebra. It is used to list the attribute desired in the result of query.
27. Define from?
The from clauses corresponds to Cartesian –product operation of the relational
algebra. It list the relations to be scanned in the evaluation of the expression.

9. 28. Define where?
The where clauses corresponds to selection predicate the relational algebra.
29. Write query for rename operation?
The query is old- name as new-name. eg:
select customer- name ,borrower .loan- number ,amount
from borrower, Loan
where borrower .loan -number =loan. Loan- number.
The result of this query is a relation with following attributes:
Customer –name ,loan-number, amount.
30. Define tuple variable?
The as clause is particularly useful in defining the notion of tuple variables, as is
done in the tuple relational calculus. A tuple variable in SQL must be associated with a
particular relation. Tuple variable are defined in the from clause by way of the as clause.
UNIT-III
1.what is integrity constraint?
Integrity constraint ensure that changes made to the database by authorized users
do not result in a loss of data consistency.
2. what is domain constraint?
Domain constraint are the most elementary form of integrity constraint they are tested
easily by the system whenever a new data item is entered into database
3. what is referential integrity?
To ensure a a value that appears in one relation for a given set of attributes also
appears for certain set of attributes in another relation.
4.what is database modification?
 insert
 delete
 update

10. 5. what is referential integrity in SQL?
Foreign key can be specified as a part of the sql ‘create table’ statement by using
the foreign key clause. A. foreign key references the primary key attributes of the
referenced table.
Example:
Create table stud ( rno number (2),status varchar(5), foreign key(no) references student
(regno));
6.what is assertions?
An assertion is a predicate expressing a condition that we wish the database always to
satisfy.
An assertion in sol takes the form,
Query:
Create assertion<assertion-name>check<predicate>
7.what is a trigger?
A trigger is a statement that the system executes automatically as a side effect of a
modification to the database. There are two requirements to design a trigger mechanisms
 specify when a trigger is to executed. This is broken up into an event that causes
the trigger to be checked and a condition that must be satisfied for trigger
execution to proceed.
 specify the actions to be taken when the trigger executes.
8.why triggers are needed?
Trigger are useful mechanisms for altering humans or for staring certain task
automatically when certain conditions are met.
9. When not to use to trigger?
Triggers should not be used
 When an insert trigger on a relation has an action that causes another insert action
to be stimulated.
 Long chain of tiggers should not be used, because it considers them as error.
10. What is security?

11. Data stored in the database need protection from unauthorization acces and malicious
destruction.
11. what is security violation?
 Unauthorized reading of data.
 Unauthorized modification of data
 Unauthorized destruction of data
12. What are levels of security?
 Database system
 Operating system
 Network
 Physical
 Human
13. What are the several form of authorization?
 Read authorization-allows reading, but not modification of data
 Insert authorization- allows insertion of new data butr not modification of existing
data
 Update authorization- allows modification but not deletion of data.
 Delete authorization-allows deletion
 Index authorization-allows the creation of new relations
 Resource authorization- allows the creation of new relations
 Alteration authorization- allows the addition or deletion of attributes in a relation
 Drop authorization-allows the deletion of relations
14. What is authorization graph?
The passing of authorization from one user to another can be represented by an
authorization graph.
15. What is notion of roles?
Roles include teller, branch manager, system administrator. The notion of roles capture
the schema. The set of roles is created in the database. Authorization can be granted to
roles. Each database user is granted a set of roles.
16. What is an audit trail?
An audit trail is a log of changes(insert, delete, update) to the databse along with
information such as which user performed the change and when the change was
performed.
17. What is encryption ?
Encryption forms the basis of good schemes for authenticating users to a database.

12. The various provisions that a database may make for authorization may still not provide
sufficient protection for high sensitive data.. in such cases data may be stored in
encrypted form.
18. What are the encryption techniques?
A good encryption technique has the following techniques
 It is relatively simple for authorization users to encrypt and decrypt data.
 It depends not on the secrecy of the algorithm, but rather on a parameter of the
algorithm called the encryption key.
 Its encryption key is extremely difficult for an intruder to determine.
19. What is authentication?
It refers to the task of verifying the identity of the person./software connecting to the
database.
20. What is normalization?
The main goal of normalization is to reduce redundant data. Normalization is based on
functional dependencies.
21. What is First Normal Form?
First normal form is also called as flat file. There are no composite attributes and every
attribute is single and describe one property.
22. What is functional dependencies?
Functional dependencies play key role in differentiating good database designs from bad
database design. A functional dependency is a type of constraint that is a generalization
of the notion of key.
23. What is decomposition?
The process of decomposing a relation schema that has many attributes into several
schemas with fewer attributes is called decomposition.
24. What is Boyce Codd Normal Form?
A relation schema R is in BCNF with respect to a set F of functional dependencies if, for
all functional dependencies in F+ of the form α→β, where α C R and β C R, atleast one of
the following holds:
 α→β is a trivial functional dependency.
 α is a superkey for schema R.
25. What is Third Normal Form?

13. A relation is said to be Third normal form where all attributes in a relation tuple are not
only functionally dependent on key attributes but also dependent on non key attributes.
UNIT_IV
1.Define Access time?
It is the time for when a read or write request is issued to when data transfer
begins.
2.Define seek time?
The time for repositioning the arm is called the seek time.
3. Define the average seek time?
It is the average of the seek times, measured over a sequence of a random
requests.
4.Define rotational latency time?
If the head has reached the desired track , the time spent waiting for the sector to
be accessed appear under the head is called rotational latency time.
5. Define MTTF?
It is used to measure the reliability of the disk . the mean time to failure of a disk
is the amount of time that , on average , that expect the system to run continuously
without any failure.
6.What is meant by RAID?
A variety of disk organization techniques , collectively called Redundant Array
Of Independent Disks have been proposed to achieve improved performance and
reliability.
7.Define Redundancy?
To store extra information that is not needed normally , but that can be used in the
event of failure of the disk to rebuilt the lost information .
8. What is meant by mirroring?
The simplest approach to introducing redundancy is to duplicate every disk . This
technique is called mirroring or shadowing.
9.What is Mean time to repair?

14. It is the time it takes to replace the failed disk and to restore the data on it is called
as mean time to repair.
10.Define striping?
In multiple disk , it is used to improve the transfer rate by striping data across
multiple disk . It can be done by 2 methods.
1.Bit level Striping
2.Block level striping
11.What is bit level striping and block level striping?
Bit level striping:
Data striping consists of splitting the bits of each byte across multiple disk.
Block level striping :
Strips block across multiple disks. It treats the array of disks as a single large disk , and
gives blocks logical number.
12.What are the different levels of RAID?
RAID level 0
RAID level 1
RAID level 2
RAID level 3
RAID level 4
RAID level 5
RAID level 6
13.Define RAID level 0?
It refers to disk arrays with striping at the level of blocks but without any
redundancy.
14. Define RAID level 1 and level 2?
RAID level 1:
It refers disk mirroring with block striping.

15. RAID level 2:
It is known as memory-style error-correcting-code(ECC) organization ,
Employs parity bit.
14. Define RAID level 3 and RAID level 4 :
RAID level 3:
It is bit interleaved parity organization. It supports a lower number of IO
operations per second.
RAID level 4:
It is block interleaved parity organization , uses block level striping like RAID 0
and in addition keeps a parity block on a separate disk for corresponding block from N
other disk.
15.Define RAID level 5 and RAID level 6:
RAID level 5:
It is block interleaved distributed parity , improves on level 4 by partitioning data
and parity among all N+1 disks , instead of storing data in N is disk and parity in one
disk
RAID level 6:
It is P+Q redundancy scheme , is much like RAID level 5 but stores extra
redundant information to guard against multiple disk failures.
16.What is mean by FILE?
File is organized logically as a sequence of records . A record is a collection of
fields.
17. Define Fixed length records?
Blocks which are of fixed size is determined by the physical properties of the disk
and by the operating system , record sizes vary.
18. Define Variable length records?
It arises in database systems in several ways .
1.Storage of multiple record types in a file.

16. 2.Record type that allow variable lengths for one or more fields.
3.Record types that allow repeating fields, such as arrays or multiset.
19.Define Slotted _page structure?
It is commonly used for organizing records within a block. The actual records are
allocated contiguously in the block.
20. Define BLOB and CLOB?
BLOB: Binary large object
CLOB:Character large object.
21. What is heap file organization?
Any record can be placed anywhere in the file where there is a space for the
record .there is no ordering if records.
22.Define sequential file organization?
Records are stored in the sequential order, according to the value of search key of
each record.
23.define hashing file organization?
A hash function is computed on some attributes of each records. The result of the
hash function specifies in which block of the file the record should be placed.
24. Define Search key?
A search key is any attribute or set of attribute , it need not be the primary key or
a even a super key.
25.Define data dictionary?
The relational database system needs to maintain data about the relations, such as
schema of the relations . this information is called the data dictionary or system catalog.
Unit-V
1. What is transaction?
Transaction is a unit of a program execution that accesses and possibly updates various
data items
2. What are the types of transaction?

17. a. begin transaction b. end transaction
3. What are the properties of transaction?
 Atomicity
 Consistency
 Isolation
 durability
4. What is atomicity?
Either all the operation of the transaction are reflected properly in the database or none
are reflected properly in the database.
5. What is consistency?
Execution of the transaction in isolation preserves the consistency of the database.
6. What is isolation?
Even though multiple transaction may execute concurrently. The system guarantees every
pair of transaction Ti and Tj.. it appears to Ti that either Tj finished the execuition before
Ti started. Thus each transaction is unaware of other transaction executing concurrently
in the system.
7. What is durability?
After the transaction completes successfully the change it has made to the database
persist even if there are system failures.
8. What are the operations of the transaction?
 Read(x) –which transfers the data items x from the database to the local buffer
belonging to the transaction that executed the read operation.
 Write(x)- which transfers the data items x from the local buffer of the transaction
that executed the write back to the database.
9. What is the transaction state?
 Active
 Partially committed
 Failure
 Aborted
 Committed

18. 10.draw the state diagram of the transaction?
11. what is reduce waiting time?
Concurrent execution reduces unpredictable delays in a runnig transaction. Moreover
it is also reduces the average response time. The average time for the transaction to be
completed after it has been submitted.
12. what is serializability?
The database system must control concurrent execution of the transaction to ensure
that the database state remains consistent.
13. what are the two types of serializability?
 Conflict serializability
 View serializability
14. What is conflict serializability?
 Ii =read(q), Ij=read(q)
 Ii= read(q), Ij=write(q)
 Ii=write(q), ij=read(q)
 Ii=write(q),Ij=write(q)
15. What is view serializability?
Active
Partially
committed
failed
commited
aborted

19.  For each data item Q if transaction Ti reads the initial value of q in schedule S.
then the transaction Ti must in schedule S’ also reads the initial value Q.
 For each data item Q if the trabsaction Ti executes read(Q) in schedule S and if
that value was produced by the write(Q) operation executed by the transaction Tj.
 For each data item Q the transaction that performs the final write(Q) operation in
schedule S must perform the final write((Q) operation in schedule S’.
16. What is recoverability?
In a system that allows concurrent execution, it is necessary also to ensure that any
transaction Tj that is dependent on Ti is also aborted. To achieve this we need to place
restriction on the type of schedules permitted in the system.
17. What is cascading rollback?
The phenomenon in which single transaction failure leads to the series of transaction
rollback is called cascading rollback.