1.Define
data warehouse?
A data warehouse is a repository of multiple heterogeneous
data sources
organized
under a unified schema at a single site to facilitate management decision
making
.
(or)
A
data warehouse is a subject-oriented, time-variant and nonvolatile
collection
of data in support of management’s decision-making process.
2.What
are operational databases?
Organizations maintain large database that are updated by
daily transactions are
called
operational databases.
3.Define
OLTP?
If an on-line operational database systems is used for
efficient retrieval, efficient
storage
and management of large amounts of data, then the system is said to be on-line
transaction
processing.
4.Define
OLAP?
Data warehouse systems serves users (or) knowledge workers
in the role of data
analysis
and decision-making. Such systems can organize and present data in various
formats.
These systems are known as on-line analytical processing systems.
5.How
a database design is represented in OLTP systems?
Entity-relation model
6.
How a database design is represented in OLAP systems?
Star schema
Snowflake schema
Fact constellation schema
7.Write
short notes on multidimensional data model?
Data warehouses and OLTP tools are based on a
multidimensional data model.
This
model is used for the design of corporate data warehouses and department data
marts.
This model contains a Star schema, Snowflake schema and Fact constellation
schemas.
The core of the multidimensional model is the data cube.
8.Define
data cube?
It consists of a large set of facts (or) measures and a
number of dimensions.
9.What
are facts?
Facts are numerical measures. Facts can also be considered
as quantities by which
we
can analyze the relationship between dimensions.
10.What
are dimensions?
Dimensions are the entities (or) perspectives with respect
to an organization for
keeping
records and are hierarchical in nature.
11.Define
dimension table?
A dimension table is used for describing the dimension.
(e.g.)
A dimension table for item may contain the attributes item_ name, brand and
type.
12.Define
fact table?
Fact table contains the name of facts (or) measures as
well as keys to each of the
related
dimensional tables.
13.What
are lattice of cuboids?
In data warehousing research literature, a cube can also
be called as cuboids. For
different
(or) set of dimensions, we can construct a lattice of cuboids, each showing the
data
at different level. The lattice of cuboids is also referred to as data cube.
14.What
is apex cuboid?
The 0-D cuboid which holds the highest level of
summarization is called the apex
cuboid.
The apex cuboid is typically denoted by all.
15.List
out the components of star schema?
A large central
table (fact table) containing the bulk of data with no
redundancy.
_ A
set of smaller attendant tables (dimension tables), one for each
dimension.
16.What
is snowflake schema?
The snowflake schema is a variant of the star schema
model, where some
dimension
tables are normalized thereby further splitting the tables in to additional
tables.
17.List
out the components of fact constellation schema?
This requires multiple fact tables to share dimension
tables. This kind of schema
can
be viewed as a collection of stars and hence it is known as galaxy schema (or)
fact
constellation
schema.
18.Point
out the major difference between the star schema and the snowflake
schema?
The dimension table of the snowflake schema model may be
kept in normalized
form
to reduce redundancies. Such a table is easy to maintain and saves storage
space.
19.Which
is popular in the data warehouse design, star schema model (or)
snowflake
schema model?
Star schema model, because the snowflake structure can reduce
the effectiveness
and
more joins will be needed to execute a query.
20.Define
concept hierarchy?
A concept hierarchy defines a sequence of mappings from a
set of low-level
concepts
to higher-level concepts.
21.Define
total order?
If the attributes of a dimension which forms a concept
hierarchy such as
“street
Country
Province
or state
City
Street
Fig:
Partial order for location
22.Define
partial order?
If
the attributes of a dimension which forms a lattice such as
“day<{month
23.Define
schema hierarchy?
A
concept hierarchy that is a total (or) partial order among attributes in a
database
schema
is called a schema hierarchy.
24.List
out the OLAP operations in multidimensional data model?
_
Roll-up
_
Drill-down
_
Slice and dice
_
Pivot (or) rotate
25.What
is roll-up operation?
The
roll-up operation is also called drill-up operation which performs aggregation
on a
data cube either by climbing up a concept hierarchy for a dimension (or) by
dimension
reduction.
26.What
is drill-down operation?
Drill-down
is the reverse of roll-up operation. It navigates from less detailed data
to
more detailed data. Drill-down operation can be taken place by stepping down a
concept
hierarchy for a dimension.
27.What
is slice operation?
The
slice operation performs a selection on one dimension of the cube resulting in
a sub
cube.
28.What
is dice operation?
The
dice operation defines a sub cube by performing a selection on two (or) more
dimensions.
29.What
is pivot operation?
This
is a visualization operation that rotates the data axes in an alternative
presentation
of the data.
30.List
out the views in the design of a data warehouse?
_
Top-down view
_
Data source view
_
Data warehouse view
_
Business query view
31.What
are the methods for developing large software systems?
_
Waterfall method
_
Spiral method
32.How
the operation is performed in waterfall method?
The
waterfall method performs a structured and systematic analysis at each step
before
proceeding to the next, which is like a waterfall falling from one step to the
next.
33.How
the operation is performed in spiral method?
The
spiral method involves the rapid generation of increasingly functional
systems,
with short intervals between successive releases. This is considered as a good
choice
for the data warehouse development especially for data marts, because the turn
around
time is short, modifications can be done quickly and new designs and
technologies
can be adapted in a timely manner.
34.List
out the steps of the data warehouse design process?
_
Choose a business process to model.
_
Choose the grain of the business process
_
Choose the dimensions that will apply to each fact table record.
_
Choose the measures that will populate each fact table record.
35.Define
ROLAP?
The
ROLAP model is an extended relational DBMS that maps operations on
multidimensional
data to standard relational operations.
36.Define
MOLAP?
The
MOLAP model is a special purpose server that directly implements
multidimensional
data and operations.
37.Define
HOLAP?
The
hybrid OLAP approach combines ROLAP and MOLAP technology,
benefiting
from the greater scalability of ROLAP and the faster computation of
MOLAP,(i.e.)
a HOLAP server may allow large volumes of detail data to be stored in a
relational
database, while aggregations are kept in a separate MOLAP store.
38.What
is enterprise warehouse?
An
enterprise warehouse collects all the information’s about subjects spanning the
entire
organization. It provides corporate-wide data integration, usually from one
(or)
more
operational systems (or) external information providers. It contains detailed
data as
well
as summarized data and can range in size from a few giga bytes to hundreds of
giga
bytes,
tera bytes (or) beyond. An enterprise data warehouse may be implemented on
traditional
mainframes, UNIX super servers (or) parallel architecture platforms. It
requires
business modeling and may take years to design and build.
39.What
is data mart?
Data
mart is a database that contains a subset of data present in a data warehouse.
Data
marts are created to structure the data in a data warehouse according to issues
such
as
hardware platforms and access control strategies. We can divide a data
warehouse into
data
marts after the data warehouse has been created. Data marts are usually
implemented
on
low-cost departmental servers that are UNIX (or) windows/NT based. The
implementation
cycle of the data mart is likely to be measured in weeks rather than
months
(or) years.
40.What
are dependent and independent data marts?
Dependent
data marts are sourced directly from enterprise data warehouses.
Independent
data marts are data captured from one (or) more operational systems (or)
external
information providers (or) data generated locally with in particular department
(or)
geographic area.
41.What
is virtual warehouse?
A
virtual warehouse is a set of views over operational databases. For efficient
query
processing, only some of the possible summary views may be materialized. A
virtual
warehouse is easy to build but requires excess capability on operational
database
servers.
42.Define
indexing?
Indexing
is a technique, which is used for efficient data retrieval (or) accessing
data
in a faster manner. When a table grows in volume, the indexes also increase in
size
requiring
more storage.
43.What
are the types of indexing?
_
B-Tree indexing
_ Bit
map indexing
_
Join indexing
44.Define
metadata?
Metadata
is used in data warehouse is used for describing data about data.
(i.e.)
meta data are the data that define warehouse objects. Metadata are created for
the
data
names and definitions of the given warehouse.
45.Define
VLDB?
Very
Large Data Base. If a database whose size is greater than 100GB, then
the
database is said to be very large database.
No comments:
Post a Comment