Concurrency concepts: what is a race condition in the context of databases and multi-process systems, and when does it occur?

Introduction / Context:
Concurrency is essential for performance, but it brings hazards. A race condition is a class of concurrency bug where the outcome depends on the non-deterministic timing of events or threads. In databases and multi-process systems, this can corrupt data, violate invariants, or cause intermittent failures that are hard to reproduce.

Given Data / Assumptions:

• Multiple activities (processes/transactions/threads) run concurrently.
• They access shared state or resources.
• Synchronization is absent, incorrect, or insufficient.

Concept / Approach:
A race condition occurs when two or more concurrent activities interact in a way that the final result depends on timing; an unlucky interleaving leads to a processing error or invariant violation. In DBMS terms, isolation levels, locks, latches, and atomic operations mitigate races. Examples include lost updates, dirty reads, and non-repeatable reads—though those are further characterized by isolation anomalies.

Step-by-Step Solution:
Recognize the key: harmful interaction between concurrent activities.Identify that simply “using different files” is not a race; it may be safe.Select the definition emphasizing timing-dependent errors: option (a).

Verification / Alternative check:
Consider a shared counter incremented by two threads without atomic operations. The final value may be less than expected due to overwrites—classic race. In databases, two transactions updating the same row without proper isolation can produce a lost update, a concrete race manifestation.

Why Other Options Are Wrong:

• Different files at the same time: Not inherently problematic; isolation may not be required.
• both (a) and (b) / All of the above: Overinclusive; (b) is not necessarily an error scenario.
• None of the above: Incorrect because (a) defines a race condition.

Common Pitfalls:
Assuming any concurrency equals a race; ignoring that proper locking or transactional isolation can prevent races; conflating race conditions with deadlocks (which are different phenomena).

Final Answer:
Two concurrent activities interact to cause a processing error