INF3703 TEST PAPER ANSWERS AND QUESTIONS
SET A+
✔✔Suppose your database system has failed. Describe the database recovery process
- ✔✔Recovery restores a database from a given state, usually inconsistent, to a
previously consistent state.
Depending on the type and the extent of the failure, the recovery process ranges from a
minor short-term inconvenience to a major long-term rebuild action. Regardless of the
extent of the required recovery process, recovery is not possible without backup.
The database recovery process generally follows a predictable scenario
1. Determine the type and the extent of the required recovery.
2. If the entire database needs to be recovered to a consistent state, the recovery uses
the most recent backup copy of the database in a known consistent state.
3. The backup copy is then rolled forward to restore all subsequent transactions by
using the transaction log information.
4. If the database needs to be recovered, but the committed portion of the database is
usable, the recovery process uses the transaction log to "undo" all the transactions that
were not committed.
✔✔A fully distributed database management system must perform all of the functions of
a centralized DBMS. What are the functions? - ✔✔1. Receive the request of an
application or end user.
2. Validate, analyze, and decompose the request. The request might include
mathematical and logical operations such as the following: Select all customers with a
balance greater than $1,000. The request might require data from only a single table, or
it might require access to several tables.
3. Map the request's logical-to-physical data components.
, 4. Decompose the request into several disk I/O operations.
5. Search for, locate, read, and validate the data.
6. Ensure database consistency, security, and integrity.
7. Validate the data for the conditions, if any, specified by the request.
8. Present the selected data in the required format
✔✔Using your own world, explain what a data fragmentation is and describe the three
data fragmentation strategies - ✔✔In a database, data fragmentation allows distributed
database designer to break a single object (for example user's database, system
database or a table) into two or more segments or fragments that are stored at any site
over a computer network.
The three data fragmentation strategies are: Horizontal fragmentation:
Division of a relation into subsets (fragments) of tuples (rows)
Vertical fragmentation: Division of a relation into attribute (column) subsets
Mixed fragmentation: Combination of horizontal and vertical strategies
✔✔Briefly explain the three (3) levels of distribution transparency - ✔✔Fragmentation
transparency: this is the highest level of transparency. The end user or programmer
does not need to know that a database is partitioned. Therefore, neither fragment
names nor fragment locations are specified prior to data
access
Location transparency: it exists when the end user or programmer must specify the
database fragment names, but does not need to specify where those fragments are
located
Local mapping transparency : exists when the end user or programmer must specify
both the fragment names and their locations
✔✔"Big data" is one of the emerging concepts in database management systems. What
do you understand by big data and what are its basic components? - ✔✔Big data is a
complex and large set of structured and unstructured data that are incapable of being
stored and processed by current technologies and infrastructures.-It is normally divided
into various components referred to as BigData "v's'':
The first "v" is normally attributed to Volume of data that is available from difference
sources. This data continues to grow.
SET A+
✔✔Suppose your database system has failed. Describe the database recovery process
- ✔✔Recovery restores a database from a given state, usually inconsistent, to a
previously consistent state.
Depending on the type and the extent of the failure, the recovery process ranges from a
minor short-term inconvenience to a major long-term rebuild action. Regardless of the
extent of the required recovery process, recovery is not possible without backup.
The database recovery process generally follows a predictable scenario
1. Determine the type and the extent of the required recovery.
2. If the entire database needs to be recovered to a consistent state, the recovery uses
the most recent backup copy of the database in a known consistent state.
3. The backup copy is then rolled forward to restore all subsequent transactions by
using the transaction log information.
4. If the database needs to be recovered, but the committed portion of the database is
usable, the recovery process uses the transaction log to "undo" all the transactions that
were not committed.
✔✔A fully distributed database management system must perform all of the functions of
a centralized DBMS. What are the functions? - ✔✔1. Receive the request of an
application or end user.
2. Validate, analyze, and decompose the request. The request might include
mathematical and logical operations such as the following: Select all customers with a
balance greater than $1,000. The request might require data from only a single table, or
it might require access to several tables.
3. Map the request's logical-to-physical data components.
, 4. Decompose the request into several disk I/O operations.
5. Search for, locate, read, and validate the data.
6. Ensure database consistency, security, and integrity.
7. Validate the data for the conditions, if any, specified by the request.
8. Present the selected data in the required format
✔✔Using your own world, explain what a data fragmentation is and describe the three
data fragmentation strategies - ✔✔In a database, data fragmentation allows distributed
database designer to break a single object (for example user's database, system
database or a table) into two or more segments or fragments that are stored at any site
over a computer network.
The three data fragmentation strategies are: Horizontal fragmentation:
Division of a relation into subsets (fragments) of tuples (rows)
Vertical fragmentation: Division of a relation into attribute (column) subsets
Mixed fragmentation: Combination of horizontal and vertical strategies
✔✔Briefly explain the three (3) levels of distribution transparency - ✔✔Fragmentation
transparency: this is the highest level of transparency. The end user or programmer
does not need to know that a database is partitioned. Therefore, neither fragment
names nor fragment locations are specified prior to data
access
Location transparency: it exists when the end user or programmer must specify the
database fragment names, but does not need to specify where those fragments are
located
Local mapping transparency : exists when the end user or programmer must specify
both the fragment names and their locations
✔✔"Big data" is one of the emerging concepts in database management systems. What
do you understand by big data and what are its basic components? - ✔✔Big data is a
complex and large set of structured and unstructured data that are incapable of being
stored and processed by current technologies and infrastructures.-It is normally divided
into various components referred to as BigData "v's'':
The first "v" is normally attributed to Volume of data that is available from difference
sources. This data continues to grow.
