cyclic information flow

garbage read

a database returns an object version not produced by any write, often from corruption or race conditions

lost update

a committed transaction's effects are lost due to another transaction's concurrent write to the same object (P4)

dirty read

one transaction reads data written by another before that transaction has completed (P1)

non-repeatable read

a transaction modifies data that another ongoing transaction previously read (P2)

phantom read

one transaction modifies rows matching a predicate that another ongoing transaction had read (P3)

stale read

an operation begins after another ends but appears to execute before the prior operation