READ UNCOMMITTED
The isolation level that provides the least amount of protection between transactions. Queries employ a locking strategy that allows them to proceed in situations where they would normally wait for another transaction. However, this extra performance comes at the cost of less reliable results, including data that has been changed by other transactions and not committed yet (known as dirty read). Use this isolation level only with great caution, and be aware that the results might not be consistent or reproducible, depending on what other transactions are doing at the same time. Typically, transactions with this isolation level do only queries, not insert, update, or delete operations.
See also ACID.
See also dirty read.
See also isolation level.
See also locking.
See also transaction.