Which three are the advantages of Distributed Database? (Choose three)

A distributed database system offers several key advantages over a centralized one.
1. Increased Availability (A): Data is often replicated across multiple sites (nodes). If one site fails due to a hardware or network issue, the system can continue to operate using data from other available sites, significantly enhancing fault tolerance and overall availability.
2. Easier Expansion (B): The architecture is modular. To increase storage or processing capacity, new servers can be added to the network without requiring a complete system overhaul. This concept, known as modular or incremental growth, makes expansion more manageable and cost-effective.
3. Improved Performance (D): Performance is enhanced in two main ways. First, data can be stored physically closer to the users who access it most frequently, reducing network latency (data localization). Second, complex queries can be broken down and executed in parallel across multiple machines, reducing the total query response time.

C. Easy to scale: While distributed databases are designed for scalability, this option is less precise than "Easier Expansion." The process of managing a large-scale distributed system, ensuring consistency and handling complex coordination, is not inherently "easy." "Easier Expansion" more accurately describes the specific advantage of modular growth. ---

1. Özsu, M. T., & Valduriez, P. (2020). Principles of Distributed Database Systems (4th ed.). Springer.

Page 6, Section 1.3.2, "Increased Reliability and Availability": "If one site fails, the DDBMS can continue to operate at a reduced level... Availability is the probability that the system is continuously available... In a distributed system, the failure of one or a few sites, or the failure of some communication links, does not render the entire system inoperable." (Supports option A)

Page 7, Section 1.3.4, "Easier System Expansion": "In a distributed environment, it is much easier to accommodate increasing database sizes. Major system overhauls are seldom necessary; expansion can usually be handled by adding processing and storage power to the network..." (Supports option B)

Page 7, Section 1.3.3, "Improved Performance": "A query that involves data from several sites can be split into subqueries that are executed in parallel at these sites... Furthermore, since the data is placed closer to its points of use, the communication delays... are minimized." (Supports option D)

2. Silberschatz, A., Korth, H. F., & Sudarshan, S. (2020). Database System Concepts (7th ed.). McGraw-Hill.

Page 910, Section 19.1.2, "Reliability and Availability": "In a distributed system, if one site fails, the remaining sites may be able to continue operating. If the data are replicated, the failure of a site does not necessarily imply the shutdown of the system." (Supports option A)

Page 910, Section 19.1.2, "Speedup of Query Processing": "If a query involves data at several sites, the query can be broken down into subqueries that can be executed in parallel at each site. The parallel computation allows for faster query processing..." (Supports option D)

3. Ramakrishnan, R., & Gehrke, J. (2003). Database Management Systems (3rd ed.). McGraw-Hill.

Page 709, Section 22.1.1, "Advantages of Distributed Databases": "Increased Availability: If a site goes down in a distributed DBMS, the other sites can continue to operate... By replicating data, we can ensure that the failure of a single site does not make the data inaccessible." (Supports option A)

Page 709, Section 22.1.1, "Advantages of Distributed Databases": "Easier Local and Global Expansion: In a distributed DBMS, it is easier to accommodate an increase in the size of the database. If a company opens a new branch, it can easily add a new site to the distributed DBMS." (Supports option B)