Degrees of isolation (degrees of Consistency)

Degrees of isolation:

degree 0 - a transaction does not overwrite data updated by another user or process ("dirty data") of other transactions

degree 1 - degree 0 plus a transaction does not commit any writes until it completes all its writes (until the end of transaction)

degree 2 - degree 1 plus a transaction does not read dirty data from other transactions

degree 3 - degree 2 plus other transactions do not dirty data read by a transaction before the transaction commits