Explain database transactions and ACID

Q: Explain database transactions and ACID

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Question

Database Transactions and ACID under Concurrency

Prompt

You are working with a relational database that supports transactions and multiple isolation levels. Explain:

The ACID properties of transactions:
- Define atomicity, consistency, isolation, and durability.
How common isolation levels differ and which anomalies they prevent:
- Isolation levels: read uncommitted, read committed, repeatable read, serializable.
- Anomalies: dirty reads, non-repeatable reads, phantom reads.
How commits and rollbacks work in practice (including the effect on visibility and durability).
How MVCC (multi-version concurrency control) helps achieve isolation.
Provide a concrete example:
- A simple schema.
- A sequence of statements from two concurrent sessions that demonstrates correct transactional usage under concurrency (i.e., no anomalies), and briefly explain why it works.

Assume a mainstream RDBMS (e.g., PostgreSQL or MySQL/InnoDB). If behavior differs by engine, note the typical difference briefly.

Explain database transactions and ACID

Database Transactions and ACID under Concurrency

Prompt

Solution (Locked)

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