This rule ensures that either every part of a task happens, or none of it does. It prevents situations where a job is only half-finished.

The All-or-Nothing Rule

This ensures the database always follows specific rules and stays in a correct state. It stops broken or invalid data from being saved.

Keeping Data Valid

This allows many people to use the database at once without interfering with each other. Each person's work stays separate until it is finished.

Working in Private

Once a task is finished and saved, the information is safe forever. Even if the power goes out, the data stays exactly where it should be.

Saving for Good

If an error happens halfway through a task, the system can automatically reset everything. This brings the data back to how it was before the task started.

The Undo Button

This is the moment the database officially saves all your changes. After this step, the work is complete and can be seen by others.

Finalizing Your Work

Sending money involves lowering one balance and raising another. These rules ensure that money never 'vanishes' if the computer fails mid-transfer.

The Bank Transfer Example

Without these safety rules, data could become messy, incorrect, or lost. They create trust that the information you see is always accurate.

Why Reliability Matters

This explains how the database manages many people making changes at the same time. It ensures that nobody's updates accidentally overwrite someone else's work.

The Bank Transfer Challenge