Release consistency is one of the consistency model

Consistency model

In computer science, consistency models are used in distributed systems like distributed shared memory systems or distributed data stores . The system supports a given model, if operations on memory follow specific rules...

s used in the domain of the concurrent programming (e.g. in distributed shared memory

Distributed shared memory

Distributed Shared Memory , in Computer Architecture is a form of memory architecture where the memories can be addressed as one address space...

, distributed transaction

Distributed transaction

A distributed transaction is an operations bundle, in which two or more network hosts are involved. Usually, hosts provide transactional resources, while the transaction manager is responsible for creating and managing a global transaction that encompasses all operations against such resources...

s etc.).

Systems of this kind are characterised by the existence of two special synchronisation operations, release and acquire. Before issuing a write to a memory object a node must acquire the object via a special operation, and later release it. Therefore the application that runs within the operation acquire and release constitutes the critical region

Mutual exclusion

Mutual exclusion algorithms are used in concurrent programming to avoid the simultaneous use of a common resource, such as a global variable, by pieces of computer code called critical sections. A critical section is a piece of code in which a process or thread accesses a common resource...

. The system is said to provide release consistency, if all write operations by a certain node are seen by the other nodes after the former releases the object and before the latter acquire it.

There are two kinds of coherence protocols that implement release consistency:

• eager, where all coherence actions are performed on release operations, and
• lazy, where all coherence actions are delayed until after a subsequent acquire