Asked by: Arsenia Mohaiemen
asked in category: General Last Updated: 21st March, 2020

Why does locking prevent dirty reads?

A write lock allows dirty reads, by other transactions and by the current transaction itself. In other words, the transaction can read its own uncommitted changes.

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Hereof, how does locking prevent dirty reads?

The transaction releases read locks when it moves off the current row. It holds write locks until it is committed or rolled back. The transaction waits until rows write-locked by other transactions are unlocked; this prevents it from reading any "dirty" data.

One may also ask, what are phantom reads? A phantom read occurs when, in the course of a transaction, two identical queries are executed, and the collection of rows returned by the second query is different from the first. Simple examples: User A runs the same query twice.

which transaction isolation level allows for dirty reads?

Read Uncommitted –

What is phantom read problem?

A phantom read occurs when, in the course of a transaction, two identical queries are executed, and the collection of rows returned by the second query is different from the first. Simple examples: User A runs the same query twice.

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