Part 125: Isolation Levels: Read Uncommitted & Read Committed

Understanding the lower isolation levels.

1. Read Uncommitted

• Allows Dirty Reads. Lowest isolation, highest throughput.
• Rarely used in production systems due to data corruption risks.

2. Read Committed (The Industry Default!)

• Default in PostgreSQL, Oracle, and SQL Server.
• Guarantees you only read committed data (prevents dirty reads).
• Uses MVCC (Multi-Version Concurrency Control): Reads never block writes, and writes never block reads!

SET TRANSACTION ISOLATION LEVEL READ COMMITTED;

Key Takeaways

• READ COMMITTED prevents dirty reads with excellent concurrency through MVCC.

In Part 126, we examine ANSI SQL Isolation Levels: Repeatable Read & Serializable!