The XA interface is the bidirectional interface between a transaction manager and resource managers. This document extends the XA interface (as defined in The XA Specification (C193)) to support communication resource managers. XA+ is a superset of XA. This Version 2 Snapshot supersedes the previous version (S201) published in 1993. Since that version the Transaction Manager Switch and facilities to pass timeout values were added and the introductory chapters of the specification were aligned with Distributed TP: Reference Model, Version 2 (G307).