Deck 12: Distributed Databases

Question 1

Which of the following is an advantage to data replication?

A) Reliability
B) Fast response
C) Node decoupling
D) All of the above

Answer 1

D

Question 2

Which of the following characterizes homogeneous environments?

A) Contains simple pathways
B) Same DBMS used at all locations
C) Some users require only local access
D) Cross-linked systems easily communicate

Answer 2

B

Question 3

Which of the following environments uses the same DBMS at each node with a central or master DBMS coordinating database access across nodes?

A) Centralized; maximum
B) Centralized; minimum
C) Homogeneous; nonautonomous
D) Federated; nonautonomous

Answer 3

C

Question 4

________ is a design goal for a distributed database,which says a user does not need to know the location of data to use the data.

A) Location transparency
B) Location autonomy
C) Location dependency
D) Distributed locatability

Question 5

Which of the following environments uses a different DBMS at each node,and supports local databases for unique data requests?

A) Gateways; local
B) Centralized; minimum
C) Homogeneous; cross-linked
D) Heterogeneous; federated

Question 6

One way to generate store and forward messages for completed transactions to be broadcast across a network is through the use of:

A) stored procedures.
B) triggers.
C) functions.
D) SQL statements.

Question 7

An integrated partition strategy is ________ to manage.

A) excellent
B) difficult
C) easy
D) medium

Question 8

Which of the following are business conditions that encourage the use of distributed databases?

A) Business unit autonomy
B) Data sharing needs
C) Data communication reliability
D) All of the above

Question 9

All of the following are advantages of vertical partitioning EXCEPT:

A) efficiency.
B) security.
C) ease of querying.
D) easier to set up than horizontal partitioning.

Question 10

Which of the following is true about horizontal partitioning?

A) Data can be stored to optimize local access.
B) Data are less secure.
C) There is consistent access speed.
D) None of the above

Question 11

Which of the following supports a simple path to other databases,without the benefits of one logical database?

A) Linked; differential
B) Gateways
C) Autonomous; cross-linked
D) Federated; nonautonomous

Question 12

All of the following are disadvantages of data replication EXCEPT:

A) storage requirements.
B) reduced network traffic at prime time.
C) complexity and cost of updating.
D) none of the above.

Question 13

Snapshot replication is most appropriate for:

A) a data warehouse application.
B) an application where the processing of data follows a workflow across the business units.
C) a transaction processing system.
D) none of the above.

Question 14

A synchronized replication strategy has a(n)________ reliability.

A) excellent
B) good
C) fair
D) medium

Question 15

Replication should be used when:

A) data currency and timing doesn't matter.
B) there is a highly heterogeneous network.
C) when there are no or few triggers.
D) all of the above.

Question 16

Which of the following is true of data replication?

A) Additional storage requirements
B) Faster response
C) Node decoupling
D) All of the above

Question 17

With a pull strategy of replication,the ________ node determines when a database is updated.

A) user
B) source
C) target
D) all of the above

Question 18

Which of the following is true of distributed databases?

A) Less reliable
B) Better local control
C) Slower response time
D) None of the above

Question 19

A(n)________ is a database stored on multiple computers in multiple locations that are NOT connected by a data communications link.

A) distributed database
B) decentralized database
C) unlinked database
D) data repository

Question 20

A centralized strategy has ________ expandability.

A) excellent
B) good
C) poor
D) medium

Question 21

A ________ allows a single SQL statement to refer to tables in more than one remote DBMS.

A) distributed UOW
B) join SQL statement
C) distributed request
D) data transfer command

Question 22

Users of distributed database systems always need to know the location of the data.

Question 23

________ insures that a transaction is successfully completed or else it is aborted.

A) Failure protocol
B) TCP/IP protocol
C) Commit protocol
D) None of the above

Question 24

Distributed databases make data sharing more difficult because of the data communication problems.

Question 25

With ________,users can act as if all the data were located at a single node.

A) location transparency
B) local autonomy
C) client-based control
D) all of the above

Question 26

A distributed database must:

A) keep track of data locations.
B) present a single logical database that is physically distributed.
C) provide consistency among data copies.
D) all of the above.

Question 27

In a homogeneous environment,the same DBMS is used at each location.

Question 28

A design goal for distributed databases that states that although a distributed database runs many transactions,it appears that a given transaction is the only one in the system is called:

A) linear run.
B) concurrency transparency.
C) transaction CPU transparency.
D) location transparency.

Question 29

A design goal for distributed databases to allow programmers to treat a data item replicated at several sites as though it were at one site is called:

A) location transparency.
B) replication accessibility.
C) replication transparency.
D) data accessibility.

Question 30

Local autonomy means that data are not accessible from remote sites.

Question 31

In a heterogeneous environment,not all users use the same DBMS.

Question 32

An optimization strategy that allows sites that can update to proceed and other sites to catch up is called:

A) read-only commit.
B) lazy commit.
C) sequenced commit.
D) linear set up.

Question 33

The sequence of instructions required to process a transaction is called the:

A) unit of work.
B) logical program unit.
C) rollback.
D) commit.

Question 34

In a distributed database,a transaction that requires reference to data at one or more nonlocal sites is called a ________ transaction.

A) link
B) tight
C) global
D) loose

Question 35

Which of the following are factors in deciding on database distribution strategies?

A) Organizational forces
B) Frequency of data access
C) Reliability needs
D) All of the above

Question 36

A joining operation in which only the joining attribute from one site is transmitted to the other site is called a(n):

A) attribute linkup.
B) key data element transfer.
C) key data element join.
D) semijoin.

Question 37

A distributed database is not just a collection of files.

Question 38

Distributed databases do not easily satisfy both transaction and analytical processing systems.

Question 39

With ________ all of the actions of a transaction are either committed or not committed.

A) location transparency
B) replication transparency
C) failure transparency
D) commit transparency

Question 40

The step in which a distributed database decides the order in which to execute the distributed query is called:

A) decomposition.
B) localization.
C) step optimization.
D) none of the above.

Question 41

A local transaction is one that requires reference only to data that are stored at the site where the transaction originates.

Question 42

Organizational forces such as funding availability drive the choice of distributed database strategy.

Question 43

Location transparency is used to inform users of where data are located within the distributed database.

Question 44

Replicated databases usually result in tightly coupled nodes.

Question 45

A replicated database with snapshots is very manageable.

Question 46

Replication is often used for noncollaborative data.

Question 47

Replication should not be used if timely updates are important.

Question 48

Shared ownership of data is most appropriate as business activities move across time zones.

Question 49

A distributed database may require more costly and complex software than a centralized database.

Question 50

Applications that can tolerate out-of-date data are not the best candidates for data replication.

Question 51

Replication transparency allows a programmer or user to treat a replicated data item as if it were a single item at a single node.

Question 52

A transaction manager is an algorithm that coordinates updates or aborts them.

Question 53

With an asynchronous distributed database,all data across the network is continuously kept up-to-date.

Question 54

A distributed DBMS must provide consistency among copies of data across the remote sites.

Question 55

Horizontal partitioning offers increased efficiency because data are close to use areas.

Question 56

Combining data across vertical partitions is generally more difficult than combining across horizontal partitions.

Question 57

The reliability of a decentralized distributed database system with independent partitions is poor.

Question 58

One way to generate messages for near-real-time replication is through the use of database triggers.

Question 59

The overriding principle in distributed database design is that data should be stored at one central site.

Question 60

Applications such as decision support or data warehousing often do not require current data and are supported by periodic snapshots.

Question 61

Simple paths to other databases without the benefits of one logical database are called ________.

Question 62

Failure transparency is a design goal for distributed databases that guarantees that all the actions associated with a transaction are either committed or none of them are committed.

Question 63

Data localization involves transforming a query into fragments that explicitly reference data at one site.

Question 64

________ is an application that can effectively employ snapshot replication in a distributed environment.

Question 65

The purpose of time-stamping is to allow transactions to be processed in parallel.

Question 66

A(n)________ is a single logical database spread physically across computers in multiple locations that are connected by a data communications link.

Question 67

In a(n)________ replication strategy,the target,not the source,controls when a local database is updated.

Question 68

An environment in which data are distributed across all nodes,and there is a global schema,is called a(n)________ environment.

Question 69

A distributed request allows a single SQL statement to refer to tables in more than one remote DBMS.

Question 70

In a semijoin,all of the selected attributes from every selected row are transmitted to each site.

Question 71

With a two-phase commit strategy for synchronizing distributed data,committing a transaction is faster than if the originating location were able to work alone.

Question 72

________ is a design goal for a distributed database that says a site can independently administer and operate its database.

Question 73

In a homogeneous distributed database environment,all users access the database through one ________.

Question 74

________ enables a user to access data without knowing exactly where the data are located.

Question 75

Two-phase commit is an algorithm for coordinating deletions in a distributed database management system.

Question 76

When separate copies of data are stored at each of two or more sites,it is called ________.

Question 77

A form of distributed database in which all data across a network are kept continuously updated,so a user can access any data anywhere on the network and get the same answer is called a(n)________ distributed database.

Question 78

A remote unit of work allows updates at the single remote computer.

Question 79

A distributed unit of work does not support location transparency.

Question 80

Concurrency transparency allows each transaction to appear as if it were the only activity in a distributed database management system.