Three-phase commit protocol

So, imagine you were playing with three friends and you all want to go on a big adventure, but you have to make sure everyone is ready at the same time so you can all leave together. This is similar to what the three-phase commit protocol is used for in computer programming.

First, everyone agrees on what they want to do, like go on an adventure. This is called the "prepare" phase. In computer programming, this means that all the databases involved in a transaction (like updating a bank account) make sure they have all the information they need to proceed.

Next, everyone checks if they can actually go on the adventure, like making sure they have enough time and resources. This is called the "pre-commit" phase. In computer programming, this means that all the databases double-check that they are able to complete their part of the transaction.

If everyone is good to go, they all give a signal to each other, like saying "ready, set, go!" in unison. This is the "commit" phase where everyone actually goes on the adventure. In computer programming, this means that all the databases actually make the changes to the data like updating the bank account.

But sometimes, someone can't go on the adventure even though they said they were ready. Maybe they forgot something important or they got sick. This is called a "failure". In computer programming, this means that one of the databases couldn't complete their part of the transaction.

If this happens, the group has to decide what to do. Maybe they cancel the adventure altogether or maybe they go on a different adventure instead. This is called the "abort" phase. In computer programming, this means that the databases have to undo the changes they made and go back to the state they were in before the transaction started.

The three-phase commit protocol is like a plan so everyone knows what they have to do and what to do if something goes wrong when multiple databases need to work together to update data.