DISTRIBUTED DATABASES QUIZ

Which of the following is true concerning a global transaction?

The required data are located in at least one nonlocal site and the distributed DBMS routes requests as necessary.

The required data are at one local site and the distributed DBMS passes the request to only the local DBMS.

The required data are located in at least one nonlocal site and the distributed DBMS passes the request to only the local DBMS.

The required data are at one local site and the distributed DBMS routes requests as necessary.

TRUE ANSWER : ?
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The purpose of timestamping is to avoid the use of locks.

False

True

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An increasingly popular option for data distribution as well as for fault tolerance of any database is to store a separate copy of the database at each of two or more sites.

True

False

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An autonomous homogenous environment is which of the following?

A different DBMS is at each node and each DBMS works independently.

The same DBMS is at each node and a central DBMS coordinates database access.

A different DBMS is at each node and a central DBMS coordinates database access.

The same DBMS is at each node and each DBMS works independently.

TRUE ANSWER : ?
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A transaction manager is which of the following?

Maintains before and after database images

Maintains a log of transactions

Maintains appropriate concurrency control

All of these

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Replication may use either synchronous or asynchronous distributed database technologies, although asynchronous technologies are more typical in a replicated environment.

False

True

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A heterogeneous distributed database is which of the following?

A different DBMS is used at each location and data are not distributed across all nodes.

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

The same DBMS is used at each location and data are not distributed across all nodes.

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

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The cost to perform a snapshot refresh may depend on whether the snapshot is simple or complex.

False

True

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Asynchronous technology can result in unsatisfactorily slow response time because the distributed DBMS is spending considerable time checking that an update is accurately and completely propagated across the network.

True

False

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A semijoin is which of the following?

Only the joining attributes are sent from one site to another and then all of the rows are returned.

All of the attributes are sent from one site to another and then only the required rows are returned.

All of the attributes are sent from one site to another and then only the required rows are returned.

Only the joining attributes are sent from one site to another and then only the required rows are returned.

TRUE ANSWER : ?
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