Definition check: Are databases stored at multiple locations without any interconnecting network still considered “distributed databases”, or does distribution imply networked coordination among sites?
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AIncorrect
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BCorrect
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CCorrect only when locations are in the same building
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DCorrect if backups are shipped via portable media
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EDepends on whether replication is enabled
Answer
Correct Answer: Incorrect
Explanation
Introduction / Context:Distributed databases coordinate a single logical database across multiple networked sites. This question tests whether merely having databases in many places—without networking—meets the definition of “distributed.”
Given Data / Assumptions:
- Multiple computers store related data sets.
- No network connectivity or distributed DBMS services exist between them.
- Goal of distributed systems: transparency (location, fragmentation, replication) via coordinated software.
Concept / Approach:Distribution implies coordination. A distributed DBMS provides a unified interface, concurrency control, and recovery across nodes. Physically separated but unconnected databases are simply independent databases, not parts of a distributed database. Tape/drive sneaker-net copies do not create distribution; they create replicas or backups without online coordination.
Step-by-Step Solution:
Check for a single logical schema spanned across sites.Verify network connectivity enabling distributed query, concurrency, and recovery.If absent, recognize the systems as separate, not distributed.Add a distributed layer (e.g., sharding, replication) to achieve true distribution.Verification / Alternative check:Run a cross-site transaction. If there is no facility for two-phase commit, distributed queries, or global catalogs, the environment is not a distributed database.
Why Other Options Are Wrong:
- Marking “Correct” confuses geographic dispersion with distributed database architecture.
- Building location or portable media do not satisfy the defining characteristics.
- Replication may exist without exposing a single logical database, but true distributed DBMSs coordinate more than copies.
Common Pitfalls:Assuming offsite backups form a distributed DB; they do not provide distributed concurrency or transparency.
Final Answer:Incorrect