What is the essence of transaction verification if it either succeeds or fails?

Transaction verification is important, even though a transaction is either successfully completed or rolled back, because:

1. Confirmation of success: It is necessary to ensure that all operations within the transaction are indeed committed, especially in distributed systems.

2. Error handling: If the transaction fails, it is important to handle the error correctly to avoid data inconsistency.

3. Repeatability: In some cases, it is required to check the transaction status for re-execution or compensation.

4. Logging and auditing: Verification helps keep track of and audit actions, which is important for security and debugging.

Thus, transaction verification is not just about checking "whether it was completed or not," but a set of actions to ensure data integrity, consistency, and reliability.