DBMS

Free Transactions and concurrency lessons

7 lessons, about 1½ hours in all. Each teaches one idea with a visual, then gives you a problem or a few questions on it. Read the lessons here, then create a free account to practise and keep your progress.

Start free with lesson 1 See the full Transactions and concurrency path

Stage 0All or nothing

Transactions and ACIDSee what goes wrong when a multi-step change is interrupted, and the four guarantees a transaction gives.13 min
The write-ahead logSee how a sequential log of changes lets the database undo unfinished work and redo committed work after a crash.14 min

Stage 1Many users at once

Schedules and serializabilityInterleave two transactions, find which operations conflict, and test whether the result equals some serial order.15 min
Isolation levels and anomaliesMeet the four classic anomalies, and the isolation levels that trade correctness against concurrency.15 min

Stage 2Control and recovery

Locks and two-phase lockingSee how shared and exclusive locks, taken in two phases, guarantee serializable schedules.14 min
Deadlocks and MVCCSee how locking can deadlock and how the database breaks it, and how keeping old versions lets readers avoid waiting.15 min
Checkpoints and crash recoverySee how checkpoints bound recovery work, and the order of the analysis, redo and undo passes.13 min

All of Transactions and concurrency is free

That’s the whole topic, from the first idea to the mastery stage, with no card needed. Create a free account to practise, keep your progress and carry on to the next topic.

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