Transaction Isolation Levels Impact

Imagine managing money in a bank. When you transfer funds, you don't want the money to disappear or duplicate. This is where transactions come in!

A transaction is a sequence of operations performed as a single logical unit of work. It either completely succeeds (commits) or completely fails (rolls back).

Transactions ensure database reliability through ACID properties:

• Atomicity: All or nothing.
• Consistency: Valid state before and after.
• Isolation: Concurrent transactions don't interfere.
• Durability: Committed changes are permanent.

When multiple users or applications access the database at the same time, strange things can happen without proper control. These are called concurrency anomalies:

• Dirty Read: Reading uncommitted data from another transaction.
• Non-Repeatable Read: Reading the same row twice in one transaction, but getting different values because another transaction committed a change in between.
• Phantom Read: Rerunning a query and seeing new rows (or missing rows) that another transaction committed.

Isolation levels help prevent these issues.