Distributed Databases Questions and Answers

Q: Which of the following is not one of the stages in the evolution of distributed DBMS?

Correct answer: Unit of workThe recognised stages are remote unit of work, distributed unit of work and distributed request, in order of increasing capability - from a transaction touching one remote site, to one touching several, to a single statement spanning several. A plain unit of work is the centralised case and is not a stage in the evolution at all.

Q: Synchronization for pull replication is less disruptive and occurs only when needed by each site, not when a central master site thinks it is best to update.

Correct answer: TrueWith pull replication each site requests a refresh when it wants one, so the update happens when the receiving site is ready rather than when a master decides. This spreads the load and avoids interrupting a site at an inconvenient moment, at the cost of the sites being less predictably in step.

Q: A distributed database has which of the following advantages over a centralized database?

Correct answer: Modular growthA distributed system can be extended by adding a site, without replacing or resizing a central machine, so capacity grows in steps matched to demand. The other three options are the recognised disadvantages: the software costs more, is more complex, and can respond more slowly where a query has to reach several sites.

Q: With asynchronous technology, if any copy of a data item is updated anywhere on the network, the same update is immediately applied to all other copies or it is aborted.

Correct answer: FalseImmediate application of every update to every copy, or abort, describes synchronous technology. Asynchronous replication is defined by the opposite: the update is applied locally and propagated later, so the copies are temporarily inconsistent. The statement has given the definition of one under the name of the other.

Q: A distributed unit of work allows various statements within a unit of work to refer to multiple remote DBMS locations.

Correct answer: TrueA distributed unit of work allows the statements within one transaction to address different remote sites, though each individual statement is still directed at a single site. Lifting that last restriction - letting one statement span several sites - is the next stage, the distributed request.

Q: Each site (or node) in a distributed system is subject to the same types of failure as in a centralized system.

Correct answer: TrueEvery site still has its own disks, processors, power and software, and can fail in all the ways a centralised system can. What distribution adds is failures of its own - a lost network link, a partitioned network, a site unreachable but still running - so the total number of ways to fail is greater, not smaller.

11.

Which of the following is not one of the stages in the evolution of distributed DBMS?

A.Unit of work
B.Remote unit of work
C.Distributed unit of Work
D.Distributed request

Answer: A

Correct answer: Unit of work

The recognised stages are remote unit of work, distributed unit of work and distributed request, in order of increasing capability - from a transaction touching one remote site, to one touching several, to a single statement spanning several. A plain unit of work is the centralised case and is not a stage in the evolution at all.

Discuss in Forum

12.

A heterogeneous distributed database is which of the following?

A.The same DBMS is used at each location and data are not distributed across all nodes.
B.The same DBMS is used at each location and data are distributed across all nodes.
C.A different DBMS is used at each location and data are not distributed across all nodes.
D.A different DBMS is used at each location and data are distributed across all nodes.

Answer: D

Correct answer: A different DBMS is used at each location and data are distributed across all nodes.

Heterogeneous means the sites run different products, and the difficulty is exactly that: differing SQL dialects, data types, transaction models and catalogue structures must be reconciled before a single query can span them. Homogeneity is easier to manage but is often not available, since sites arrive through acquisition and separate history.

Discuss in Forum

13.

Which of the following is a disadvantage of replication?

A.Reduced network traffic
B.If the database fails at one site, a copy can be located at another site.
C.Each site must have the same storage capacity.
D.Each transaction may proceed without coordination across the network.

Answer: C

Correct answer: Each site must have the same storage capacity.

A full copy of the database at every site means every site must be able to hold the whole thing, which can be a heavy requirement at a small location. The other three options are advantages of replication rather than disadvantages - less network traffic, resilience to the failure of one site, and local processing without network coordination.

Discuss in Forum

14.

Synchronization for pull replication is less disruptive and occurs only when needed by each site, not when a central master site thinks it is best to update.

A.True
B.False

Answer: A

Correct answer: True

With pull replication each site requests a refresh when it wants one, so the update happens when the receiving site is ready rather than when a master decides. This spreads the load and avoids interrupting a site at an inconvenient moment, at the cost of the sites being less predictably in step.

Discuss in Forum

15.

A homogenous distributed database is which of the following?

A.The same DBMS is used at each location and data are not distributed across all nodes.
B.The same DBMS is used at each location and data are distributed across all nodes.
C.A different DBMS is used at each location and data are not distributed across all nodes.
D.A different DBMS is used at each location and data are distributed across all nodes.

Answer: B

Correct answer: The same DBMS is used at each location and data are distributed across all nodes.

Homogeneous means one product throughout, which removes the translation problems of a heterogeneous system: the same dialect, the same data types, the same transaction semantics. It is the easier case to build and administer, and it is realistic only where the organisation controls every site.

Discuss in Forum

16.

A distributed database has which of the following advantages over a centralized database?

A.Software cost
B.Software complexity
C.Slow Response
D.Modular growth

Answer: D

Correct answer: Modular growth

A distributed system can be extended by adding a site, without replacing or resizing a central machine, so capacity grows in steps matched to demand. The other three options are the recognised disadvantages: the software costs more, is more complex, and can respond more slowly where a query has to reach several sites.

Discuss in Forum

17.

With asynchronous technology, if any copy of a data item is updated anywhere on the network, the same update is immediately applied to all other copies or it is aborted.

A.True
B.False

Answer: B

Correct answer: False

Immediate application of every update to every copy, or abort, describes synchronous technology. Asynchronous replication is defined by the opposite: the update is applied locally and propagated later, so the copies are temporarily inconsistent. The statement has given the definition of one under the name of the other.

Discuss in Forum

18.

A distributed unit of work allows various statements within a unit of work to refer to multiple remote DBMS locations.

A.True
B.False

Answer: A

Correct answer: True

A distributed unit of work allows the statements within one transaction to address different remote sites, though each individual statement is still directed at a single site. Lifting that last restriction - letting one statement span several sites - is the next stage, the distributed request.

Discuss in Forum

19.

A distributed database is which of the following?

A.A single logical database that is spread to multiple locations and is interconnected by a network
B.A loose collection of file that is spread to multiple locations and is interconnected by a network
C.A single logical database that is limited to one location.
D.A loose collection of file that is limited to one location.

Answer: A

Correct answer: A single logical database that is spread to multiple locations and is interconnected by a network

Two conditions must both hold. It must be a single logical database, so users see one coherent whole rather than several separate ones; and the sites must be connected by a network, or nothing can be combined. Separate databases on separate machines are a decentralised system, not a distributed database.

Discuss in Forum

20.

Each site (or node) in a distributed system is subject to the same types of failure as in a centralized system.

A.True
B.False

Answer: A

Correct answer: True

Every site still has its own disks, processors, power and software, and can fail in all the ways a centralised system can. What distribution adds is failures of its own - a lost network link, a partitioned network, a site unreachable but still running - so the total number of ways to fail is greater, not smaller.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Distributed Databases Questions and Answers || Distributed Databases MCQ Questions and Answers || Distributed Databases GK Questions and Answers || Distributed Databases GK MCQ Questions || Distributed Databases Multiple Choice Questions and Answers || Distributed Databases GK || GK on Distributed Databases || Database Questions and Answers || Database MCQ Questions and Answers || Database GK Questions and Answers || GK on Database

Distributed Databases Questions and Answers

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications