Editing Isolation (database systems) (section)

===Read committed===
In this isolation level, a lock-based [[concurrency control]] DBMS implementation keeps write locks (acquired on selected data) until the end of the transaction, but read locks are released as soon as the [[Select (SQL)|SELECT]] operation is performed (so the '''''[[#Non-repeatable reads|non-repeatable reads phenomenon]]''''' can occur in this isolation level). As in the previous level, ''range-locks'' are not managed.

Putting it in simpler words, read committed is an isolation level that guarantees that any data read is committed at the moment it is read. It simply restricts the reader from seeing any intermediate, uncommitted, 'dirty' read. It makes no promise whatsoever that if the transaction re-issues the read, it will find the same data; data is free to change after it is read.