To improve data integrity in a distributed processing environment, APPC/MVS, together with RRS, participates in the two-phase commit protocol to provide recovery for transaction programs. The two-phase commit protocol is a set of actions that resource managers and a syncpoint manager perform to ensure that a program's updates to distributed resources are coordinated. Through this protocol, a series of resource updates are treated as an atomic action; that is, the updates are either all made (committed) or not made (backed out).

In z/OS, your installation can enable APPC/MVS logical units (LUs) to act as resource managers. The resources they manage, or protect, are the conversations established between APPC/MVS transaction programs and their partner TPs. To identify their conversations as protected resources, the TPs allocate the conversations with a synchronization level of syncpt. When one of the TPs is ready to commit or back out its changes for a particular unit of work, the TP issues either the Commit or Backout callable service to begin a syncpoint operation. During this operation, the local and partner LUs work with system syncpoint managers to coordinate the changes; RRS is the system syncpoint manager for APPC/MVS LUs.