• Table of contents

A transaction is an indivisible logical unit of work in a database management system, allowing you to represent multiple operations as a single step. Operations executed by transactions include reading and writing database records. A database transaction has to preserve atomicity, consistency, isolation, and durability [this].

ACID definition in DDIA notes.

Components in transactions

⮑ Transaction manager

Coordinates, schedules, and tracks transactions.

• more specific explanation for chatgpt

⮑ Lock manager

Prevents concurrent access to data.

• Shared (S) lock: multiple transactions can ONLY READ data at the same time.
• Exclusive (X) lock: one transaction can access the data at a time.

⮑ Page cache

Intermediary between persistent storage (disk) and storage engine (see “Buffer management”).

⮑ Log manager

Stores history of all operations on cached pages that haven’t been scyned to persistent storage so it isn’t lost (WAL - write ahead log).