Within a DBMS, what are the core responsibilities of a Transaction Manager (consider logging, recovery, and concurrency)?

Introduction / Context:
The transaction manager enforces ACID properties in database systems. It coordinates logging, recovery, and isolation so that committed work is durable and concurrent activities do not corrupt data.

Given Data / Assumptions:

• Transactions need atomicity and durability (logging, recovery).
• Isolation requires concurrency control (locks, MVCC).
• System failures must be recoverable using logs and images.

Concept / Approach:
A transaction manager typically maintains a transaction log, stores before/after images (or logical redo/undo information), and enforces concurrency control via locking or MVCC to achieve isolation levels.

Step-by-Step Solution:

Verification / Alternative check:
DBMS architecture references consistently list logging/recovery and locking/MVCC under the transaction subsystem.

Why Other Options Are Wrong:

• A/B/C alone are partial; D captures the complete set.

Common Pitfalls:
Believing logging alone guarantees isolation; without concurrency control, anomalies can occur.

Final Answer:
All of the above.