Phenomena - Data problem

> (Data|State) Management and Processing > Data Properties and Transactions

1 - About

If several transactions concurrently read from and write to a database, the following problems called phenomena can arise:

The isolation levels are defined in terms of this phenomena (problem) that must be prevented between concurrently executing transactions.


3 - List

3.1 - Dirty reads

A transaction reads data that has been written by another transaction that has not been committed yet.

See Dirty read

3.2 - Non repeatable (fuzzy) reads

A user queries a row and then later queries the same row, only to discover that the data has changed.

See Fuzzy reads (Non repeatable read)

3.3 - Phantom reads

A transaction reruns a query returning a set of rows that satisfies a search condition and finds that another committed transaction has inserted additional rows that satisfy the condition.

Phantom read/update problem

3.4 - Dirty Write