Deadlocks and Concurrency Strategies
Learn how to identify, prevent, and handle deadlocks to ensure smooth concurrent database operations.
We'll cover the following...
Imagine our OnlineStore is running a massive flash sale. Two customer service representatives are simultaneously processing orders and updating customer information. Representative A begins updating a customer’s loyalty points and locks their record.
Meanwhile, Representative B starts updating the stock for a product that this same customer just ordered, locking the product record.
Now, Representative A needs to update the product stock to finalize the order—but it’s locked by B. At the same time, Representative B needs access to the customer’s record to add their loyalty points—but it’s locked by A. Both representatives are now stuck, waiting for the other to finish, yet neither can proceed.
The system freezes.
This frustrating situation is called a deadlock, and it’s a serious challenge in any multi-user database system. In this lesson, we’ll explore how deadlocks occur, why they matter, and how to design systems that prevent them—ensuring smooth database operations even when multiple transactions happen simultaneously.
By the end of this lesson, we will be able to:
Understand what a deadlock is and the conditions that cause it.
Explore various strategies for handling deadlocks, including prevention and detection methods.
Compare different concurrency strategies to manage simultaneous data access effectively.
Let’s get started and learn how to keep our database operations running without getting stuck in a digital traffic jam.
What is a deadlock?
In a busy database system, multiple transactions often need to access the same resources, like tables or rows.
To maintain data integrity, the system uses locks to ensure that only one transaction can modify a piece of data at a time. While essential, this locking mechanism can lead to a serious problem: the deadlock. A deadlock is a state in which two or more transactions are blocked indefinitely, each waiting for the other to release a lock.
Because all transactions are waiting, none of them can proceed, effectively halting a part of the system. Deadlocks can severely impact an application’s performance and reliability. If transactions are stuck, users might experience frozen screens, timeouts, and errors. For our ...