CS1301-DATABASE
MANAGEMENT SYSTEMS
TWO MARKS:
UNIT: 1
INTRODUCTION AND CONCEPTUAL MODELLING
1. Define database management system?
Database
management system (DBMS) is a collection of interrelated data and a
set of programs to access those data.
2. List
any eight applications of DBMS.
a)
Banking, b) Airlines, c) Universities, d) Credit card transactions
e)
Tele communication, f) Finance, g) Sales, h) Manufacturing,
i)
Human resources.
3. What
are the disadvantages of file processing system?
The disadvantages of file processing
systems are
a)
Data redundancy and inconsistency, b) Difficulty in accessing data
c)
Data isolation, d) Integrity problems, e) Atomicity problems
f)
Concurrent access anomalies.
4. What
are the advantages of using a DBMS?
The advantages of using a DBMS are
a) Controlling redundancy, b)
Restricting unauthorized access
c) Providing multiple user interfaces, d)
Enforcing integrity constraints.
e) Providing back up and recovery.
5. Give
the levels of data abstraction?
a)
Physical level, b) logical level, c) view level.
6.
Define instance and schema?
Instance: Collection
of data stored in the data base at a particular moment is
called an Instance of the database.
Schema: The
overall design of the data base is called the data base schema.
7.
Define the terms 1) physical schema 2) logical schema.
Physical schema: The
physical schema describes the database design at the
physical
level, which is the lowest level of abstraction describing how the data are actually stored.
Logical schema: The
logical schema describes the database design at the logical
level,
which describes what data are stored in the database and what relationship
exists among the data.
8. What
is conceptual schema?
The schemas at
the view level are called subschemas that describe different views
of the database.
9.
Define data model?
A data model is
a collection of conceptual tools for describing data, data
relationships,
data semantics and consistency constraints.
10.
What is storage manager?
A storage
manager is a program module that provides the interface between the
low
level data stored in a database and the application programs and queries
submitted to the system.
11.
What are the components of storage manager?
The
storage manager components include
a)
Authorization and integrity manager,
b)
Transaction manager, c) File manager, d) Buffer manager.
12.
What is the purpose of storage manager?
The
storage manager is responsible for the following
a)
Interaction with him files manager,
b)
Translation of DML commands in to low level files system commands,
c)
Storing, retrieving and updating data in the database.
13. List the data structures implemented by the storage manager.
The storage
manager implements the following data structure
a) Data files, b)
Data dictionary, c) indices.
14.
What is a data dictionary?
A data
dictionary is a data structure which stores Meta data about the structure of
the database i.e.
the schema of the database.
15.
What is an entity relationship model?
The entity
relationship model is a collection of basic objects called entities and
relationship
among those objects. An entity is a thing or object in the real world that is distinguishable
from other objects.
16.
What are attributes? Give examples.
An entity is
represented by a set of attributes. Attributes are descriptive properties
possessed by
each member of an entity set.
Example: possible
attributes of customer entity are customer name, customer id,
customer street,
customer city.
17.
What is relationship? Give examples
A
relationship is an association among several entities.
Example: A
depositor relationship associates a customer with each account that
he/she
has.
18.
Define the terms
i) Entity set
ii) Relationship set
Entity
set: The set of all entities of the same type is termed
as an entity set.
Relationship
set: The set of all
relationships of the same type is termed as a
relationship set.
19.
Define single valued and multi valued attributes.
Single
valued attributes:
Attributes with a single value for a particular entity are
called
single valued attributes.
Multi
valued attributes: Attributes with
a set of value for a particular entity are
called multi valued attributes.
20.
What are stored and derived attributes?
Stored
attributes: The attributes
stored in a data base are called stored attributes.
Derived
attributes: The attributes that are derived from the stored
attributes are
called derived attributes.
21.
What are composite attributes?
Composite
attributes can be divided in to sub parts.
22.
Define null values.
In
some cases a particular entity may not have an applicable value for an
attribute
Or
if we do not know the value of an attribute for a particular entity. In these
cases null value is used.
23.
Define the terms
i) Entity type, ii) Entity set
Entity
type: An entity type defines a collection of entities that
have the same
attributes.
Entity
set: The set of all entities of the same type is termed
as an entity set.
24.
What is meant by the degree of relationship set?
The degree of
relationship type is the number of participating entity types.
25.
Define the terms
i) Key
attribute, ii) Value set
Key attribute: An entity type usually has an attribute
whose values are distinct
from
each individual entity in the collection. Such an attribute is called a key attribute.
Value set: Each
simple attribute of an entity type is associated with a value set
that
specifies the set of values that may be assigned to that attribute for each individual entity.
26.
Define weak and strong entity sets?
Weak
entity set:
entity set that do not have key attribute of their own are called
weak entity sets.
Strong
entity set:
Entity set that has a primary key is termed a strong entity set.
27.
What does the cardinality ratio specify?
Mapping
cardinalities or cardinality ratios express the number of entities to which
another
entity can be associated. Mapping cardinalities must be one of the
following:
•
One to one • One to many
•
Many to one • Many to many
28.
Explain the two types of participation constraint.
• Total: The
participation of an entity set E in a relationship set R is said to
be total if every entity in E participates in at least one
relationship in R.
• Partial: If
only some entities in E participate in relationships in R, the
participation of entity set E in
relationship R is said to be partial.
29.
Define the terms
i) DDL, ii) DML
DDL: Data base schema is specified by a set
of definitions expressed by a special
language called a data definition
language.
DML: A data manipulation language is a
language that enables users to access or
manipulate data as organized by the
appropriate data model.
30.
Write short notes on relational model
The relational
model uses a collection of tables to represent both data and the
relationships
among those data. The relational model is an example of a record
based model.
31.
Define tuple and attribute
• Attributes: column headers • Tuple: Row
32. Define the term relation.
Relation is a
subset of a Cartesian product of list domains.
33.
Define tuple variable
Tuple variable
is a variable whose domain is the set of all tuples.
34.
Define the term Domain.
For each
attribute there is a set of permitted values called the domain of that
attribute.
35.
What is a candidate key?
Minimal super
keys are called candidate keys.
36.
What is a primary key?
Primary key is chosen by the database designer as
the principal means of
identifying
an entity in the entity set.
37.
What is a super key?
A
super key is a set of one
or more attributes that collectively allows us to
identify
uniquely an entity in the entity set.
38.
Define- relational algebra.
The
relational algebra is a procedural query language. It consists of a set of
operations
that take one or two relation as input and produce a new relation as
output.
39.
What is a SELECT operation?
The
select operation selects
tuples that satisfy a given predicate. We use the
lowercase
letter s to denote selection.
40.
What is a PROJECT operation?
The
project operation is a unary operation that returns its argument relation with
certain
attributes left out. Projection is denoted by pie (p).
41.
Write short notes on tuple relational calculus.
The
tuple relational calculation is anon procedural query language. It describes
the
desired information with out giving a specific procedure for obtaining that
information.
A
query or expression can be expressed in tuple relational calculus as
{t
| P (t)}
Which
means the set of all tuples‘t’ such that predicate P is true for‘t’.
Notations
used:
•
t [A] ® the value of tuple ‘t’ on attribute, A
•
t Î r ® tuple ‘t’ is in relation ‘r’
•
$ ® there exists
Definition
for ‘there exists’ ($):
$
t Î r(Q(t))
which
means there exists a tuple ‘t’ in relation ‘r’
Such
that predicate Q (t) is true.
•
" ® for all
Definition
for ‘for all’ ("):
"t
Î r(Q(t))
Which
means Q (t) is true for all tuples‘t’ in relation
‘r’.
•
_ ® Implication
Definition
for Implication (_):
P_Q
means if P is true then Q must be true.
42. Write
short notes on domain relational calculus
The domain relational calculus uses
domain variables that take on values from an
attribute domain rather than values for
entire tuple.
43.
Define query language?
A
query is a statement requesting the retrieval of information. The portion of
DML
that involves information retrieval is called a query language.
44.
Write short notes on Schema diagram.
A
database schema along with primary key and foreign key dependencies can be
depicted
pictorially by schema diagram. Each relation appears as a box with
attributes
listed inside it and the relation name above it.
45.
What is foreign key?
A
relation schema r1 derived from an ER schema may include among its
attributes
the primary key of another relation schema r2.this attribute is called a foreign key from r1 referencing
r2.
UNIT:
2
RELATIONAL
MODEL
1. What
are the parts of SQL language?
The SQL language has several
parts:
_ Data - definitition language
_ Data manipulation language
_ View definition
_ Transaction control
_ Embedded SQL
_ Integrity
_ Authorization
2. What
are the categories of SQL command?
SQL commands are divided in to
the following categories:
1. Data - definitition language, 2.
Data manipulation language
3. Data Query language, 4. Data
control language
5. Data administration statements,
6. Transaction control statements
3. What
are the three classes of SQL expression?
SQL expression consists of three
clauses:
_ Select _ From
_ where
4. Give
the general form of SQL query?
Select A1, A2…………., An
From R1, R2……………, Rm
Where P
5. What
is the use of rename operation?
Rename
operation is used to rename both relations and a attributes.
It
uses the as clause, taking the form:
Old-name
as new-name
6.
Define tuple variable?
Tuple
variables are used for comparing two tuples in the same relation. The tuple
variables
are defined in the from clause
by way of the as clause.
7. List
the string operations supported by SQL?
1) Pattern matching Operation, 2)
Concatenation,
3) Extracting character strings, 4)
Converting between uppercase and lower case letters.
8. List
the set operations of SQL?
1) Union, 2) Intersect operation,
3) The except operation.
9. What
is the use of Union and intersection operation?
Union: The result of this operation includes
all tuples that are either in r1 or in r2
or in both r1 and r2.Duplicate tuples are
automatically eliminated.
Intersection: The
result of this relation includes all tuples that are in both r1 and
r2.
10.
What are aggregate functions? And list the aggregate functions supported by
SQL?
Aggregate
functions are functions that take a collection of values as input and
return
a single value.
Aggregate
functions supported by SQL are
_
Average: avg _ Minimum: min _ Maximum: max
_
Total: sum _ Count: count
11.
What is the use of group by clause?
Group by clause is used to apply aggregate
functions to a set of tuples.The
attributes
given in the group by clause are
used to form groups.Tuples with the
same
value on all attributes in the group by
clause are placed in one group.
12.
What is the use of sub queries?
A
sub query is a select-from-where expression that is nested with in another
Query.
A common use of sub queries is to perform tests for set membership, make
Setcomparisions, and determine
set cardinality.
13.
What is view in SQL? How is it defined?
Any
relation that is not part of the logical model, but is made visible to a user
as a
virtual
relation is called a view.
We
define view in SQL by using the create
view command. The form of the
create view command is
Create
view v as <query expression>
14.
What is the use of with clause in SQL?
The
with clause provides a way of
defining a temporary view whose definition is
available
only to the query in which the with clause
occurs.
15.
List the table modification commands in SQL?
_ Deletion, _ Insertion, _ Updates, _
Update of a view
16.
List out the statements associated with a database transaction?
_ Commit work_ Rollback work
17.
What is transaction?
Transaction is a unit of program
execution that accesses and possibly updated
various data items.
18.
List the SQL domain Types?
SQL
supports the following domain types.
1)
Char (n) 2) varchar (n) 3) int 4) numeric (p, d)
5)
float (n) 6) date.
19.
What is the use of integrity constraints?
Integrity
constraints ensure that changes made to the database by authorized users
do
not result in a loss of data consistency. Thus integrity constraints guard
against
accidental
damage to the database.
20.
Mention the 2 forms of integrity constraints in ER model?
_ Key declarations, _ Form of a
relationship
21.
What is trigger?
Triggers
are statements that are executed automatically by the system as the side
effect
of a modification to the database.
22.
What are domain constraints?
A
domain is a set of values that may be assigned to an attribute .all values that
appear
in a column of a relation must be taken from the same domain.
23.
What are referential integrity constraints?
A
value that appears in one relation for a given set of attributes also appears
for a
certain
set of attributes in another relation.
24.
What is assertion? Mention the forms available.
An
assertion is a predicate expressing a condition that we wish the database
always
to satisfy. _ Domain integrity
constraints._ Referential integrity constraints.
25.
Give the syntax of assertion?
Create assertion <assertion
name>check<predicate>
26. What is the need for
triggers?
Triggers are useful mechanisms
for alerting humans or for starting certain tasks
automatically when certain
conditions are met.
27.
List the requirements needed to design a trigger.
The requirements
are
_ Specifying when a trigger is to
be executed.
_ Specify the actions to be taken
when the trigger executes.
28.
Give the forms of triggers?
_ The triggering event can be
insert or delete.
_ For updated the trigger can
specify columns.
_ The referencing old row as
clause
_ The referencing new row as
clause
_ The triggers can be initiated
before the event or after the event.
29.
What does database security refer to?
Database
security refers to the protection from unauthorized access and malicious
destruction
or alteration.
30.
List some security violations (or) name any forms of malicious access.
_
Unauthorized reading of data
_
Unauthorized modification of data
_
Unauthorized destruction of data.
31.
List the types of authorization.
_
Read authorization, _ Write authorization
_
Update authorization, _ Drop authorization
32.
What is authorization graph?
Passing
of authorization from one user to another can be represented by an
authorization
graph.
33.
List out various user authorization to modify the database schema.
_ Index authorization, _ Resource
authorization
_ Alteration authorization, _ Drop authorization
34.
What are audit trails?
An
audit trail is a log of all changes to the database along with information such
as
which user performed the change and when the change was performed.
35.
Mention the various levels in security measures.
_
Database system, _ Operating system
_
Network, _ Physical, _ human.
36.
Name the various privileges in SQL?
_
Delete, _ Select, _ Insert, _ update.
37.
Mention the various user privileges.
_
All privileges directly granted to the user or role.
_
All privileges granted to roles that have been granted to the user or role.
38.
Give the limitations of SQL authorization.
_
The code for checking authorization becomes intermixed with the rest of the
application code.
_
Implementing authorization through application code rather than specifying it
declaratively in SQL makes it hard to ensure
the absence of loopholes.
39.
Give some encryption techniques?
_
DES, _ AES, _ Public key encryption.
40.
What does authentication refer?
Authentication
refers to the task of verifying the identity of a person.
41.
List some authentication techniques.
_ Challenge response scheme, _
Digital signatures
_ Nonrepudiation.
42.
Define 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. _->_, where _.
43.
List the disadvantages of relational database system
_
Repetition of data, _ Inability to represent certain information.
44.
What is first normal form?
The domain of attribute must include
only atomic (simple, indivisible) values.
45.
What is meant by functional dependencies?
Consider
a relation schema R and _ C R and _ C R. The functional dependency _
_
_ holds on relational schema R if in any legal relation r(R), for all pairs of
tuples
t1 and t2 in r such that t1 [_] =t1 [_], and also t1 [_] =t2 [_].
46.
What are the uses of functional dependencies?
_
To test relations to see whether they are legal under a given set of functional
dependencies.
_
To specify constraints on the set of legal relations.
47.
Explain trivial dependency?
Functional dependency of the form
_ _ _ is trivial if _ C _. Trivial functional
dependencies are satisfied by all
the relations.
48.
What are axioms?
Axioms
or rules of inference provide a simpler technique for reasoning about
functional
dependencies.
49.
What is meant by computing the closure of a set of functional dependency?
The closure of F denoted by F+ is
the set of functional dependencies logically
implied by F.
50.
What is meant by normalization of data?
It
is a process of analyzing the given relation schemas based on their Functional
Dependencies
(FDs) and primary key to achieve the properties
_
Minimizing redundancy, _ Minimizing insertion, deletion and updating anomalies.
51.
Define canonical cover?
A
canonical cover Fc for F is a set of dependencies such that F logically implies
all
dependencies in FC and Fc logically implies all dependencies in F. Fc must
have
the following properties.
52.
List the properties of canonical cover.
Fc must have the following properties.
_ No functional dependency in Fc
contains an extraneous attribute.
_ Each left side of a functional
dependency in Fc is unique.
53.
Explain the desirable properties of decomposition.
_
Lossless-join decomposition, _ Dependency preservation
_
Repetition of information.
54.
What is 2NF?
A relation schema R is in 2NF if it is
in 1NF and every non-prime attribute A in R
is fully functionally dependent on
primary key.
UNIT:
3
DATA
STORAGE AND QUERY PROCESSING
1. What is an index?
An index is a structure that helps to
locate desired records of a relation quickly,
without examining all records
.
2. Define query optimization.
Query optimization refers to the process
of finding the lowest –cost method of
evaluating a given query.
3. What are called jukebox systems?
Jukebox systems contain a few drives and
numerous disks that can be loaded into
one of the drives automatically.
4. What are the types of storage devices?
_
Primary storage, _ Secondary storage, _ Tertiary storage
_
Volatile storage, _ Nonvolatile storage.
5. What
is called remapping of bad sectors?
If
the controller detects that a sector is damaged when the disk is initially
formatted,
or when an attempt is made to write the sector, it can logically map the sector
to a different physical location.
6.
Define access time.
Access
time is the time from when a read or write request is issued to when data
transfer
begins.
7.
Define seek time.
The time for repositioning the arm is
called the seek time and it increases with the
distance that the arm is called the seek
time.
8.
Define average seek time.
The average seek time is the average of
the seek times, measured over a sequence
of random requests.
9.
Define rotational latency time.
The time spent waiting for the sector to
be accessed to appear under the head is
called the rotational latency time.
10.
Define average latency time.
The average latency time of the disk is
one-half the time for a full rotation of the
disk.
11.
What is meant by data-transfer rate?
The data-transfer rate is the rate at
which data can be retrieved from or stored to
the disk.
12. What
is meant by mean time to failure?
The mean time to failure is the amount
of time that the system could run
continuously without failure.
13.
What is a block and a block number?
A block is a contiguous sequence of
sectors from a single track of one platter.
Each request specifies the address on
the disk to be referenced. That address is in the
form of a block number.
14.
What are called journaling file systems?
File systems
that support log disks are called journaling file systems.
15.
What is the use of RAID?
A
variety of disk-organization techniques, collectively called redundant arrays
of
independent
disks are used to improve the performance and reliability.
16.
What is called mirroring?
The
simplest approach to introducing redundancy is to duplicate every disk. This
technique
is called mirroring or shadowing.
17.
What is called mean time to repair?
The
mean time to failure is the time it takes to replace a failed disk and to
restore
the
data on it.
18.
What is called bit-level striping?
Data
striping consists of splitting the bits of each byte across multiple disks.
This
is
called bit-level striping.
19.
What is called block-level striping?
Block
level striping stripes blocks across multiple disks. It treats the array of
disks
as
a large disk, and gives blocks logical numbers.
20.
What are the two main goals of parallelism?
_
Load –balance multiple small accesses, so that the throughput of such
accesses
increases.
_
Parallelize large accesses so that the response time of large accesses is
reduced
.
21.
What are the factors to be taken into account when choosing a RAID level?
o
Monetary cost of extra disk storage requirements.
o
Performance requirements in terms of number of I/O operations
o
Performance when a disk has failed.
o
Performances during rebuild.
22.
What is meant by software and hardware RAID systems?
RAID
can be implemented with no change at the hardware level, using only
software
modification. Such RAID implementations are called software RAID systems and
the systems with special hardware support are called hardware RAID systems.
23.
Define hot swapping?
Hot
swapping permits the removal of faulty disks and replaces it by new ones
without
turning power off. Hot swapping reduces the mean time to repair.
24.
What are the ways in which the variable-length records arise in database systems?
_
Storage of multiple record types in a file.
_
Record types that allow variable lengths for one or more fields.
_
Record types that allow repeating fields.
25.
What is the use of a slotted-page structure and what is the information present
in the header?
The
slotted-page structure is used for organizing records within a single block.
The
header contains the following information.
_
The number of record entries in the header.
_
The end of free space
_
An array whose entries contain the location and size of each record.
26.
What are the two types of blocks in the fixed –length representation? Define them.
•
Anchor block: Contains the first record of a chain.
•
Overflow block: Contains the records other than those that are the first
record
of a chain.
27.
What is known as heap file organization?
In
the heap file organization, any record can be placed anywhere in the file where
there
is space for the record. There is no ordering of records. There is a single
file for each relation.
28.
What is known as sequential file organization?
In
the sequential file organization, the records are stored in sequential order,
according
to the value of a “search key” of each record.
29.
What is hashing file organization?
In
the hashing file organization, a hash function is computed on some attribute of
each
record. The result of the hash function specifies in which block of the file
the record should be placed.
30.
What is known as clustering file organization?
In
the clustering file organization, records of several different relations are
stored
in
the same file.
31.
What are the types of indices?
_ Ordered
indices, _ Hash indices
32.
What are the techniques to be evaluated for both ordered indexing and hashing?
_
Access types, _ Access time, _ Insertion time
_
Deletion time, _ Space overhead
33.
What is known as a search key?
An
attribute or set of attributes used to look up records in a file is called a
search
key.
34.
What is a primary index?
A
primary index is an index whose search key also defines the sequential order of
the
file.
35.
What are called index-sequential files?
The
files that are ordered sequentially with a primary index on the search key, are
called
index-sequential files.
36.
What are the two types of indices?
_ Dense index, _
Sparse index
37.
What are called multilevel indices?
Indices with two
or more levels are called multilevel indices.
38.
What is B-Tree?
A
B-tree eliminates the redundant storage of search-key values .It allows search
key
values to appear only once.
39.
What is a B+-Tree index?
A
B+-Tree index takes the form of a balanced tree in which every path from the
root
of the root of the root of the tree to a leaf of the tree is of the same
length.
40.
What is a hash index?
A
hash index organizes the search keys, with their associated pointers, into a
hash
file
structure.
41.
What is called query processing?
Query
processing refers to the range of activities involved in extracting data from
a
database.
42.
What are the steps involved in query processing?
The
basic steps are:
_
parsing and translation, _ optimization, _ evaluation
43.
What is called an evaluation primitive?
A
relational algebra operation annotated with instructions on how to evaluate is
called
an evaluation primitive.
44.
What is called a query evaluation plan?
A
sequence of primitive operations that can be used to evaluate ba query is a
query
evaluation plan or a query execution plan.
45.
What is called a query –execution engine?
The
query execution engine takes a query evaluation plan, executes that plan, and
returns
the answers to the query.
46.
What are called as index scans?
Search
algorithms that use an index are referred to as index scans.
47.
What is called as external sorting?
Sorting of
relations that do not fit into memory is called as external sorting.
48.
What is called as recursive partitioning?
The
system repeats the splitting of the input until each partition of the build
input
fits
in the memory. Such partitioning is called recursive partitioning.
49.
What is called as an N-way merge?
The
merge operation is a generalization of the two-way merge used by the
standard
in-memory sort-merge algorithm. It merges N runs, so it is called an N-way merge.
50.
What is known as fudge factor?
The
number of partitions is increased by a small value called the fudge factor,
which
is usually 20 percent of the number of hash partitions computed.
UNIT:
4
TRANSACTION
PROCESSING
1. What
is transaction?
Collections
of operations that form a single logical unit of work are called
transactions.
2. What
are the two statements regarding transaction?
The
two statements regarding transaction of the form:
_
Begin transaction, _ End transaction
3. What
are the properties of transaction?
The
properties of transactions are:
_
Atomicity, _ Consistency, _ Isolation, _ Durability
4. What
is recovery management component?
Ensuring
durability is the responsibility of a software component of the base
system
called the recovery management component.
5. When
is a transaction rolled back?
Any
changes that the aborted transaction made to the database must be undone.
Once
the changes caused by an aborted transaction have been undone, then the
transaction
has been rolled back.
6. What
are the states of transaction?
The
states of transaction are
_
Active, _ Partially committed, _ Failed
_
Aborted, _ Committed, _ Terminated
7. What
is a shadow copy scheme?
It
is simple, but efficient, scheme called the shadow copy schemes. It is based on
making
copies of the database called shadow copies that one transaction is active at a
time. The scheme also assumes that the database is simply a file on disk.
8. Give
the reasons for allowing concurrency?
The
reasons for allowing concurrency is if the transactions run serially, a short
transaction
may have to wait for a preceding long transaction to complete, which can lead to
unpredictable delays in running a transaction.
So concurrent execution reduces the unpredictable delays in running
transactions.
9. What
is average response time?
The
average response time is that the average time for a transaction to be
completed
after it has been submitted.
10.
What are the two types of serializability?
The
two types of serializability is
_
Conflict serializability, _ View serializability
11.
Define lock?
Lock
is the most common used to implement the requirement is to allow a
transaction
to access a data item only if it is currently holding a lock on that item.
12.
What are the different modes of lock?
The
modes of lock are:
_
Shared, _ Exclusive
13.
Define deadlock?
Neither
of the transaction can ever proceed with its normal execution. This
situation
is called deadlock.
14.
Define the phases of two phase locking protocol
_
Growing phase: a transaction may obtain locks but not release any lock.
_
Shrinking phase: a transaction may release locks but may not obtain any new
locks.
15.
Define upgrade and downgrade?
It
provides a mechanism for conversion from shared lock to exclusive lock is
known
as upgrade.
It
provides a mechanism for conversion from exclusive lock to shared lock is
known
as downgrade.
16.
What is a database graph?
The
partial ordering implies that the set D may now be viewed as a directed
acyclic
graph, called a database graph.
17.
What are the two methods for dealing deadlock problem?
The
two methods for dealing deadlock problem is deadlock detection and
deadlock
recovery.
18.
What is a recovery scheme?
An
integral part of a database system is a recovery scheme that can restore the
database
to the consistent state that existed before the failure.
19.
What are the two types of errors?
The
two types of errors are:
_
Logical error, _ System error
20.
What are the storage types?
The
storage types are:
_
Volatile storage, _ Nonvolatile storage
21.
Define blocks?
The
database system resides permanently on nonvolatile storage, and is
partitioned
into fixed-length storage units called blocks.
22.
What is meant by Physical blocks?
The
input and output operations are done in block units. The blocks residing on
the
disk are referred to as physical blocks.
23.
What is meant by buffer blocks?
The blocks
residing temporarily in main memory are referred to as buffer blocks.
24.
What is meant by disk buffer?
The area of
memory where blocks reside temporarily is called the disk buffer.
25.
What is meant by log-based recovery?
The
most widely used structures for recording database modifications is the log.
The
log is a sequence of log records, recording all the update activities in the
database. There are several types of log
records.
26.
What are uncommitted modifications?
The
immediate-modification technique allows database modifications to be output
to
the database while the transaction is still in the active state. Data
modifications written by active transactions are called uncommitted
modifications.
27.
Define shadow paging.
An
alternative to log-based crash recovery technique is shadow paging. This
technique
needs fewer disk accesses than do the log-based methods.
28.
Define page.
The
database is partitioned into some number of fixed-length blocks, which are
referred
to as pages.
29.
Explain current page table and shadow page table.
The
key idea behind the shadow paging technique is to maintain two page tables
during
the life of the transaction: the current page table and the shadow page table.
Both the page tables are identical when the transaction starts. The current
page table may be changed when a transaction performs a write operation.
30.
What are the drawbacks of shadow-paging technique?
• Commit
Overhead, • Data fragmentation, • Garbage collection
31.
Define garbage collection.
Garbage
may be created also as a side effect of crashes. Periodically, it is
necessary
to find all the garbage pages and to add them to the list of free pages. This process
is called garbage collection.
32.
Differentiate strict two phase locking protocol and rigorous two phase locking
protocol.
In
strict two phase locking protocol all
exclusive mode locks taken by a
transaction
is held until that transaction commits.
Rigorous two phase locking protocol requires that
all locks be held until the
transaction
commits.
33. How
the time stamps are implemented
•
Use the value of the system clock as the time stamp. That is a transaction’s
time
stamp is equal to the value of the clock when the transaction enters the
system.
•
Use a logical counter that is incremented after a new timestamp has been
assigned;
that is the time stamp is equal to the value of the counter.
34.
What are the time stamps associated with each data item?
•
W-timestamp (Q) denotes the largest time stamp if any transaction that
executed
WRITE (Q) successfully.
•
R-timestamp (Q) denotes the largest time stamp if any transaction that
executed
READ (Q) successfully.
UNIT:
5
CURRENT
TRENDS
1. What
is meant by object-oriented data model?
The
object-oriented paradigm is based on encapsulation of data and code related
to
an object in to a single unit, whose contents are not visible to the outside
world.
2. What
is the major advantage of object-oriented programming paradigm?
The
ability to modify the definition of an object without affecting the rest of the
system
is the major advantage of object-oriented programming paradigm.
3. What
are the methods used in object-oriented programming paradigm?
*read-only, *update
4. What
is the main difference between read-only and update methods?
A
read-only method does not affect the values of a variable in an object, whereas
an
update method may change the values of the variables.
5. What
is the use of keyword ISA?
The
use of keyword ISA is to indicate that a class is a specialization of another
class.
6.
Differentiate sub-class and super-class?
The
specialization of a class is called subclasses.eg: employee is a subclass of
person
and teller is a subclass of employee.Conversely, employee is a super class
of
teller, and person is a super class of employee.
7. What
is substitutability?
Any
method of a class-say A can equally well be invoked with any object
belonging
to any subclasses B of A. This characteristic leads to code reuse, since
the
messages, methods, and functions do not have to be written again for objects
of
class B.
8. What
is multiple inheritance?
Multiple
inheritance permits a class to inherit variables and methods from
multiple
super classes.
9. What
is DAG?
The
class-subclass relationship is represented by a directed acyclic graph.eg:
employees
can be temporary or permanenet.we may create subclasses temporary
and
permanenet, of the class employee.
10.
What is disadvantage of multiple inheritance?
There
is potential ambiguity if the same variable or method can be inherited from
more
than one superclass.eg: student class may have a variable dept identifying a
student's
department, and the teacher class may correspondingly have a variable
dept
identifying a teacher's department.
11.
What is object identity?
An
object retains its identity even if some or all the values of variables or
definitions
of methods change overtime.
12.
What are the several forms of identity?
*Value, *Name, *Built-in
13.
What is a value?
A
data value is used for identity. This form of identity is used in relational
systems.eg:
The primary key value of a tuple identifies the tuple.
14.
What is a Name?
A
user-supplied name is used for identity. This form of identity is used for
files in
file
systems. The user gives each file a name that uniquely identifies it,
regardless
of
its contents.
15What
is a Built-in
A
notation of identity is built-into the data model or programming language and
no
user-supplied identifier is required. This form of identity is used in object-oriented
systems.
16 What
is meant by object identifiers?
Object-oriented
systems use an object identifier to identify objects. Object
identifiers
are unique: that is each object has a single identifier, and no two
objects
have the same identifier.
17.
What are composite objects?
Objects
that contain other objects are called complex objects or composite
objects.
18.
What is object containment?
References
between objects can be used to model different real-world concepts.
19. Why
containment is important in oosystems?
Containment
is an important concept in oosystems because it allows different
users
to view data at different granularities.
20.
Define object-relational systems?
Systems
that provide object-oriented extensions to relational systems are called
object-relational
systems.
21. How
persistent programming languages differ from traditional programming
languages?
Database
languages differ from traditional programming languages in that they directly manipulate
data that are persistent-that is, data that continue to exist even after the program
terminated. Relation in a database and tuples in a relation are examples of persistent
data. In contrast, the only persistent data that traditional programming languages
directly manipulate are files.
22.
Define atomic domains?
A
domain is atomic if elements of the domain are considered to be indivisible
units.
23.
Define 1NF?
First normal
form is one which requires that all attributes have atomic domains.
24.
What is nested relational model?
The
nested relational model is an extension of relational model in which domains
may
be either atomic or relation valued.
25.
List some instances of collection types?
*sets,*arrays,*multisets
26. How
to create values of structured type?
Constructor
functions are used to create values of structured types. A function
with
the same name as a structured type is a constructor function for the structured
type.
27.
Write a query to define tables students and teachers as sub tables of people?
Create
table students of student under people
Create
table teachers of teacher under people
28.
What is a homogeneous distributed database?
In
homogeneous distributed databases, all sites have identical database
management
system software, are aware of one another, and agree to cooperate in
processing
user's requests.
29. What
is a heterogeneous distributed database?
In a heterogeneous distributed
database, different sites may use different schemas,
and different dbms s/w.The sites
may not be aware of one another, and they may
provide only limited facilities
for cooperation in transaction processing.
30.
What are the two approaches to store relations in distributed database?
*Replication, *Fragmentation
31.
What are the two different schemes for fragmenting a relation?
*horizontal, *vertical
32.
What is horizontal fragmentation?
Horizontal
fragmentation splits the relation by assuming each tuple of r to one or
more
fragments.
33.
What is vertical fragmentation?
Vertical
fragmentation splits the relation by decomposing the scheme R of
relation
r.
34.
What are the various forms of data transparency?
*fragmentation
transparency, *replication transparency, *location transparency
35.
Define decision tree classifiers?
As
the name suggests decision tree classifiers use a tree: each leaf node has an
associated class, and each internal node has a predicate associated with it.
16 MARK QUESTIONS
UNIT:
1
1.
EXPLAIN ABOUT DATABASE SYSTEM STRUCTURE?
Storage manager
• Authorization and integrity
manager, • Transaction manager, • File manager,
• Buffer manager
Storage manager implements
several data structure as a part of physical system
implementation
• Data function, • Data
dictionary, • Indices
The query processor
• DDL interpreter, • DML, • Query
evaluation engine
2.
DESCRIBE RELATIONAL MODEL?
Structure of relational data base
_ Basic structure, _ Database
schema, _ Keys
_ Schema diagram, _ Query
languages
3. BRIEFLY EXPLAIN RELATIONAL ALGEBRA?
Fundamental
operations
• Unary operations, • Binary
operations
Select
operations
_branchname=’perryridge’ (loan)
The
project operation
_loannumber,amount (loan)
Composition
of relational operations
• Relational algebra expressions
Union
operations
r _ s r and s must be a same arity.
They must have the same no of
attributes.
The set
difference operations
r-s produce a relation containing
those tuples in r but not in s.
The
Cartesian product operations
The
rename operations
4. WHAT
IS DATA MODELS? EXPLAIN IT DETAIL?
Entity
relationship model
• Rectangles, • Ellipse, •
Diamonds, • Lines
Relational
model
Relational model use a collection
of tables to represent both data and the
relationships among those data.
Each table has a multiple columns and each columns has
unique name
Other
data models
• Object oriented data model, •
Object relational data model, • Network data model
• Hierarchical data model
5.
BRIEFLY DESCRIBE RELATIONAL CALCULUS?WITH SOME EXAMPLES?
The
tuple relational calculus
A query in a tuple relational
calculus is expressed as
{t| P(t)}
• Example Queries
• Formal definition
• Safety of expressions
• Expressive power of languages
The
domain relational calculus
• Example Queries
• Formal definition
• Safety of expressions
• Expressive power of languages
UNIT-2
1.
DESCRIBE INTEGRITY AND SECURITY?
• Domain constraint
Referential
integrity
A value that appears in one
relation for a given set of attributes also appear
for a certain set of attributes
in another relation. This condition is called referential
integrity.
• Referential integrity and E-R models, • Database modification
• Referential integrity in SQL
2. WHAT
IS AGGREGATE FUNCTION?BRIEFLY DESCRIBE IT?
Aggregate functions are functions
that take a collection of values as input and
return a single value. SQL offers
5 built-in aggregate functions:
• Average: avg, • Minimum:min, • Maximum: max, •
Total:sum, • Count:count
Average: avg
Select
avg (balance)
From account
Where branch-name=’perryridge’
Count :count
select branch-name,count(distinct customer-name)
from depositior,account
where depositor.account-number=account.account-number
groupby
branch-name
3. WHAT
IS DATA DEFINITION LANGUAGE?EXPLAIN IT IN DETAIL?
The SQL DDL allows specification
of not only a set of relations, but also
information after each relation,
including
• The schema for each relation
• The domain of values associated
with each attribute
• The integrity constraints
• The set of indices to be
maintained for each relation
• The security and authorization
information for each relation
• The physical storage structure
of each relation on disk
Domain
Types in SQL
Char(n),
varchar(n), int, small int,
numeric(p,d), real, double, precision,
float(n), date, time, timestamp.
Schema
Definition in SQL
• Primary key, • Check
4.
EXPLAIN MECHANISM OF NESTED QUERIES?
SQL provides a mechanism for
nesting subqueries.A subquery is a select from
where expression that is nested
within another query. A common use of sub queries is to
perform tests for set membership,
make set comparisons, and determine set cardinality.
• Set membership
(select
customer-name
from depositor)
• Set comparison
select
distinct T.branch-name
from branch as
T,branch as S
where T.assets >
S.assets and S.branch-city=’Brooklyn’
• Test for Empty Relations
Select customer-name
from borrower
where
exits (select *
from depositor
where depositor.customername=
borrower.customer-name)
• Test for the Absence of Duplicate Tuples
5.
WRITE SHORT NOTES ON MODIFICTION OF THE DATA BASE?
• Definition
delete
from r
where P
• Insertion
insert
into account
values (‘A-9732’,’perryridge’,1200)
• Updates
update account
set balance=balance*1.05
• Update of a view, • Transaction
UNIT-3
1.
DESCRIBE FILE ORGANISATION?
A file is organized logically as
a sequence of records. These records are mapped
onto disk blocks.
• Fixed-Length Records
type deposit=record
Accountnumber:char(10);
branch name:char(22);
balance: real;
end
• Variable length records
*storage of
multiple record types in a file
* Record types that allow
variable lengths for one or more fields
*Record types that allow
repeating fields
_ Byte string Representation
_ Fixed length representation
• Reserved space
• List representation
2.
DEFINE RAID? BRIEFLY EXPLAIN IT?
A variety of disk organization
techniques, collectively called redundant arrays
of independent disks (RAID)
• Improvement of reliability via
redundancy.
• Improvement in performance via
parallelism
1. Bit level striping
2. Block level striping
_ RAID levels
• RAID level 0
• RAID level 1
• RAID level 2(memory style error
correcting code)
• RAID level 3 (Bit interleaved
parity organization)
• RAID level 4 (Block interleaved
parity organization)
• RAID level 5 (Block interleaved
distributed parity)
• RAID level 6 (P+Q redundancy)
3WRITE
SHORT NOTES ON INDEX STRUCTURE OF FILES?
There are two basic kinds of
indices
• Ordered indices
• Hash indices
Each technique must be evaluated
on the basis of these factors:
• Access types
• Access time
• Insertion time
• Deletion time
• Space overhead
_ Ordered indices
_ Primary index
_ Dense and sparse indices
_ Multilevel index
_ Index update
_ Secondary indices
B+-Tree
index files
B+-Tree index structure is the
most widely used of several index structures
that maintain there efficiency
despite insertion and deletion of data.
_ Structure of B+-Tree
_ Queries on B+-Tree
_ Update on B+-Tree
_ B+-Tree file organization
_ B-Tree index files
4.
EXPLAIN HASH FILE ORGANIZATION?
Hash
functions
• The distribution is uniform
Hash functions assign each bucket
the same number of search –key
values from the set of all
possible search-key values
• The distributed in random
In the average case each bucket
will have nearly same no of
values assigned to it, regardless
of the actual distribution of search-key
values
Handling
of bucket overflows
• Insufficient buckets
• Skew
Open
hashing
Under an alternative approach
called open hashing
Close
hashing
The form of hash structure that
we have just described is something
referred to as close hashing.
Hash
indices
5. WHAT
IS MAGNETIC DISKS?EXPLAIN IT?
Magnetic disk provides the bulk
of secondary storage of modern computer
system. The disk capacity is
growing at over 50% per year. But the storage
requirements of large
applications has also been growing very fast and in some case
every faster than the growth rate
of disk capacities. A large data
base may require 100
of disks.
• Physical characteristics of
disk
Physical disks are relatively
simple. Each disc platter has a flat circular shape
We can
call magnetic disk as
• hard disk
• Floppy disk
The read write head store
information on a sector magnetically as reversals of
the direction of magnetization of
the magnetic material. There may be hundreds of
concentric tracks on a disc
surface, containing thousands of sectors.
Unit
4
1.
DESCRIBE LOG BASED RECOVERY
The most usably structure for
recording data base modification is the LOG
the log is a sequence of log
records recording all the update activities in the data base.
There are several types of log
records. An update log records describes a single data base
write it has these fields
• Transaction identifier
• Data item identifier
• Old value
• New value
The various types log records as.
• < Ti start >. Transaction
Ti has started
• < Ti , Tx v1,v2 >
.Transaction Ti has performed a right on data item
• < Ti commit > Transaction
Ti has committed
• < Ti about > Transaction
Ti has aborted
_ Deferred data base modification
_ Immediate data base modification
_ Check point
_ Shadow paging
2. WHAT
IS SERIALIZABILITY?EXPLAIN ITS TYPES?
The
data base system must control concurrent
execution
of transactions, to ensure that the data base state
remains
consistent. There are different forms of schedule
equivalence
they lead to the notions of
• Conflict serializability
• View serializability
Conflict
serializability
We say
that ii and I j conflict if they are operations by different
transaction
on the same data item and at least one of these instruction is a write
operations
View
serializability
The
concept of view equivalence leads to the concept of View
serializability
we say that a schedules S is view serializable if it is view equivalent to
a
serial scheduler
3.WRITE
SHORT NOTES ON TRANSACTION STATE?
A
transaction may not always complete its execution successfully such a
transaction
is termed aborted
A
transaction must be in one of the following states
• Active, • Partially
committed, • Failed, • Aborted, • Committed
4.
BRIEFLY DESCRIBE CONCURRENCYEXECUTION?
• Lock – based protocols, • Locks
There
are various modes in which a data item may be locked in
this
section we restrict our attention to two modes
• Shared, • Exclusive
T1 :
lock – x(B );
read(B);
B:=B-50;
write(B);
unlock(B);
Lock-x(A);
read(A);
A:=A+50;
write(A);
unlock(A).
5.
EXPLAIN CONCURRENCY CONTROL?
Concurrency
control
Oracles multiversion concurrency
control differs from the
concurrency mechanism used by
some other data base vendors. Read only queries are
given a read –consistent snapshot
which is view if the data base as it existed at the
specific point in time,
containing all update that we were committed by that point in time
and not containing any updates
that were not committed at any point in time thus read
clock are not used in read only
queries don’t interfere with other data base activity in
term of locking.
Managed
stand by data base
To ensure high availability
oracle provide a managed stand by data base
future A stand by data base is a
copy of the regular data base ie in solved on the separate
system. If a catastrophic failure
occur on the primary system, the stand by system is
activate and take over there by
minimizing effect on failure on a availability. Oracle
keeps the stand by data base up
to date by constantly applying archived redo logs that are
shipped from the primary data
base the back up data base can be brought online in readonly
mode and used for reporting and
decision support queries
UNIT
5
1.
WRITE SHORT NOTES ON DATA WARE HOUSING?
Data ware housing applications
requires the transformation of data from many
sources into a cohesive
consistent step set of data configured appropriately for use in data
ware house operation.
• Distributed Transformation services
Data ware housing is an approach
to manage data in which
heterogeneous data sources are
migrated to a separate homogeneous
data base
• Online Analytical processing services
OLAP services provide server and
client capabilities to create
and manage multidimensional OLAP
data .
2. EXPLAIN NESTED RELATIONS?
Nested relations
The assumption of INF is a
natural one in the bank examples we
have considered. However, not all
applications are best modeled by INF relations.
The nested relational model is an
extension of the relational model in which
domains may be either atomic or
relation valued.
We illustrate nested relations by
an example from a library. Suppose we store for
each book the following in
formations
• Book title, • Set of authors, •
Publishers, • Set of keywords
We can see that if we define a
relation for the preceding information, several
domains will be monatomic
• Authors, • Keywords, •
Publishers
Complex
types
Collection
and large object types
Create
table books(
…
Keyword-set setoff(varchar(20))
…
)
Structure
types
Creation
of values of complex types
3. WHAT
IS INHERITANCE? DESCRIBE IT IN DETAIL?
Inheritance
Inheritance can be at the levels
of types, or at the level of tables We first
consider inheritance of types,
then inheritance at the level of labels.
Type
inheritance
Suppose that we have the
following type definition for people
create
type person
(name varchar(20)
address varchar(20))
Table
inheritance
Create
table people
of person
The consistency requirements for
sub tables are
1. Each tuple of the sub table
can correspond to at most one tuple in each of its
immediate sub tables.
2. SQL:1999 has an additional
constraint that all the tuples corresponding to each
other must be derived from one
tuple .
Overlapping
sub tables
4 WHAT
ARE THE TYPES OF REFERENCE?EXPLAIN IT WITH SUITABLE
EXAMPLES?
Object oriented language provided
the ability to refer the object attribute of
the type can be referred to the
specified type. We can define the type dept with a field
name and a field head which is
reference to the type person and a table dept of the type
dept as followed
Create
type dept(
Name varchar(20),
Head ref(person)scope people
)
Create
table dept
of dept
The table definition must specify
that the reverence is derived and must still
specify a self referential
attribute name. When interesting a tuple for dept we can then use
Insert
into dept
Values(‘CS’,’john’)
5. DESCRIBE QUERIES WITH COMPLEX TYPES?
The present extension of the SQL
query language deal with the complex type
Let us start with the simple
example:
Find the title and the name of
the publisher of each book this query carries out the
task:
Select title,
publisher.name
From books
• path expression
The reference are dereference in 1999
by the –> simple
Select head-> name,
head->address
From dept
An expression such as”
head->name” is called the path expression.
• Collection valued attributes
• Nesting and unnesting
The
transformation of the nested relation in to a form with fewer
(or no)
the relation –valued attribute value is called unnesting
The
reverse process of transformation a INF relation into a
nested relation is called
nesting.
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