X/Open XA

What is XA

XA stands for "eXtended Architecture" and is an X/Open group standard for executing a "global transaction" that accesses more than one back-end data-store. XA specifies how a transaction manager will roll up the transactions against the different data-stores into an "atomic" transaction and execute this with the two-phase commit (2PC) protocol for the transaction. Thus, XA is a type of transaction coordination, often among databases. ACID Transactions are a key feature of databases, but typically databases only provide the ACID guarantees for activities that happen inside a single database. XA coordination allows many resources (again, often databases) to participate in a single, coordinated, atomic update operation.

In computing, the XA standard is a specification by The Open Group for distributed transaction processing (DTP). It describes the interface between the global transaction manager and the local resource manager. The goal of XA is to allow multiple resources (such as databases, application servers, message queues, transactional caches, etc.) to be accessed within the same transaction, thereby preserving the ACID properties across applications. XA uses a two-phase commit to ensure that all resources either commit or rollback any particular transaction consistently (all do the same).

The XA specification describes what a resource manager must do to support transactional access. Resource managers that follow this specification are said to be XA-compliant.

The XA specification was based on an interface used in the Tuxedo system developed in the 1980s, but adopted by several systems since then.