Question 1

Placing a complete copy of the database at every site on the distributed network maximizes availability and minimizes concurrent update problems.

Accepted Answer

Placing a complete copy of the database at every site on the distributed network may maximize availability, but it can create concurrent update problems such as data inconsistencies and conflicts. A better approach would be to use techniques like replication, partitioning, or distributed transactions to ensure data consistency and avoid conflicts.

Question 2

A distributed database management system manages the distributed data as a single, logical database.

Accepted Answer

A distributed database management system (DDBMS) manages multiple databases distributed across different locations and makes them appear as a single, logical database to the end-users. This provides the benefits of data availability, reliability, and scalability while allowing for efficient data sharing and coordination among different organizations and departments.

Question 3

One of the principles of data replication in a distributed database is to place copies of tables at the sites that use them most heavily in order to minimize telecommunications costs.

Accepted Answer

Placing copies of tables at the sites that use them most heavily helps to reduce the amount of data that needs to be transmitted over the network, which can reduce telecommunications costs. This is a common strategy in data replication for distributed databases.

Question 4

What client/server database and distributed database have in common is that in both cases the databases can be located other than "in the computer itself."

Accepted Answer

Both client/server database and distributed database can have the databases located on remote servers or machines, rather than being stored locally on the computer.

Question 5

Distributed data with no replication provides a high degree of availability.

Accepted Answer

Distributed data with no replication means that there is only one copy of the data, so if that copy becomes unavailable, the data is no longer accessible. Therefore, it does not provide a high degree of availability. Replication, on the other hand, creates multiple copies of the data, which increases availability.

Question 6

One of the principles of data replication in a distributed database is to ensure that there are at least two copies of important or frequently used tables to realize the gains in availability.

Accepted Answer

This statement is true. Data replication is used to improve the availability and accessibility of data in a distributed database. By having multiple copies of important or frequently used tables, the system can continue to function in the event of a failure or downtime in one of the nodes.

Question 7

If the nature of the data and of the applications that use it can tolerate retrieved data not necessarily being up-to-the-minute accurate, then several "synchronous" approaches to updating replicated data are appropriate.

Accepted Answer

Synchronous approaches to updating replicated data ensure that all copies of the data are updated simultaneously, which is necessary for applications that cannot tolerate inconsistencies or outdated information. If the nature of the data and applications can tolerate not being up-to-the-minute accurate, "asynchronous" approaches would be more appropriate, as they allow for updates to happen at different times, potentially improving performance and availability at the cost of immediate consistency.

Question 8

The term "client" in a local area network refers to the larger computer with the shared database that all of the PCs on the network can access.

Accepted Answer

The term "client" in a local area network refers to the individual computers or devices that request resources or services from another computer or server on the network, not the larger computer with the shared database. The larger computer is typically referred to as a server.

Question 9

One use of the term three-tier approach to client/server database is that data sought from one of the client PCs can be on any one of a succession of three other PCs on the LAN.

Accepted Answer

The term three-tier approach to client/server database typically refers to the division of responsibilities between three layers or tiers: the user interface, application logic, and database management. It does not necessarily involve a succession of PCs on a LAN for accessing data.

Question 10

When data is distributed in a distributed database arrangement, the database is no longer considered to be a single, logical database.

Accepted Answer

Even in a distributed database arrangement, the database is still considered to be a single, logical database to the user, despite its data being physically distributed across multiple locations.

Question 11

If in a distributed database network, a copy of the entire database is kept at the headquarters site and each table is replicated exactly once at any one of the other sites, there is no reason for the headquarters site to ever become a bottleneck.

Accepted Answer

Even with this replication strategy, the headquarters site can become a bottleneck due to centralized operations, updates, or queries that require access to the complete database, leading to high traffic and processing load at the headquarters.

Question 12

One of the principles of data replication in a distributed database is to maximize the number of copies of any one table to control the security and concurrency issues.

Accepted Answer

The principle of data replication in a distributed database is to balance the tradeoff between data consistency and availability by creating multiple copies of data across different servers. Maximized copies can lead to increased storage requirements and network traffic. Security and concurrency issues can be controlled through other mechanisms such as access control and locking protocols.

Question 13

In a network environment, a centralized database provides local autonomy over the data.

Accepted Answer

In a network environment, a decentralized database provides local autonomy over the data.

Question 14

In a two-tiered client/server arrangement, data can be found on each PC's hard drive and data can be in a database at the server.

Accepted Answer

In a two-tiered client/server arrangement, data can be stored on both the client's hard drive and in a database on the server.

Question 15

In one use of the term three-tier approach to client/server database the three tiers are the client PCs, servers known as "application servers" and other servers known as "database servers."

Accepted Answer

In a three-tier approach to client/server database, the three tiers are typically the client PCs, application servers, and database servers.

Question 16

In the database server approach to client/server database, the actual database processing is done at the server.

Accepted Answer

In the database server approach, the server is responsible for processing the requests and managing the database, while the client is primarily responsible for user interface and presentation of data.

Question 17

In the database server approach to client/server database, when a client computer on the LAN needs to query, update, or otherwise use a file on the server, the entire file must be sent from the server to that client.

Accepted Answer

In the database server approach, only the required subset of data is sent from the server to the client, not the entire file. This approach reduces network traffic and improves performance.

Question 18

If in a distributed database network, a copy of the entire database is kept at the headquarters site and each table is replicated exactly once at any one of the other sites, the application environment can continue to function even if the headquarters site goes down.

Accepted Answer

In this setup, because each table is replicated at least once at a site other than the headquarters, the system can continue to operate using these replicas even if the headquarters site becomes unavailable, ensuring continuity of operations.

Question 19

One use of the term three-tier approach to client/server database is that data sought from one of the client PCs can be on the client's hard drive, at the LAN server, or at a mainframe beyond the LAN.

Accepted Answer

The three-tier approach to client/server database refers to the organization of data in three tiers (or levels) - client, application server, and database server. Data can be stored at any of these levels, which includes the client's hard drive, LAN server, or mainframe beyond the LAN. Therefore, the statement is true.

Question 20

In the two-tier approach to client/server database, location transparency means that the person issuing a query at a client does not have to know whether the data is at the client or at the server.

Accepted Answer

Location transparency is a key feature of the two-tier approach to client/server database architecture where the user interacts with the client-side interface and is unaware of the location of data, i.e., whether it is stored locally on the client-side or remotely on the server-side. Therefore, the statement is true.

Quiz 12: Clientserver Database and Distributed Database