What is a transaction manager?

A transaction manager is a system component responsible for coordinating and managing transactions within a database or distributed system. Its key roles include:

1. **Transaction Coordination:** Oversees the execution of transactions, ensuring they adhere to ACID (Atomicity, Consistency, Isolation, Durability) properties.

2. **Commit and Rollback Control:** Manages commit and rollback operations to ensure that transactions are either fully completed or fully undone in case of errors or failures.

3. **Concurrency Control:** Handles concurrent access to data, managing locks and preventing conflicts between transactions to maintain data consistency.

4. **Distributed Transaction Management:** In distributed systems, coordinates transactions across multiple databases or nodes, ensuring all parts of the transaction are consistent and properly completed.

5. **Recovery Management:** Facilitates recovery in case of system failures by using logs and checkpoints to restore the system to a consistent state.

The transaction manager is crucial for ensuring that transactions are processed reliably and that the database maintains integrity and consistency.