Summary of z/OS Resource Recovery Services support

z/OS Resource Recovery Services (RRS) provides a system resource recovery platform so that applications running on z/OS can access local and distributed resources and have system coordinated recovery management of these resources.

The support includes:

• A synchronization point manager to coordinate the two-phase commit process
• Implementation of the SAA Commit and Backout callable services for use by application programs
• A mechanism to associate resources with an application instance
• Services for resource manager registration and participation in the two-phase commit process with RRS
• Services to allow resource managers to express interest in an application instance and be informed of commit and backout requests
• Services to enable resource managers to obtain system data to restore their resources to consistent state
• A communications resource manager (called APPC/PC for APPC/Protected Conversations) so that distributed applications can coordinate their recovery with participating local resource managers

• Extended Recovery Facility (XRF)

  Running protected conversations in an IMS-XRF environment does not guarantee that the alternate system can resume and resolve any unfinished work started by the active system. This process is not guaranteed because a failed resource manager must re-register with its original RRS system if the RRS is still available when the resource manager restarts. Only if the RRS on the active system is not available can an XRF alternate can register with another RRS in the sysplex and obtain the incomplete unit of recovery data of the failing active.

  Recommendation: Because IMS retains indoubt units-of-recovery indefinitely until they are resolved, switch back to the original active system as soon as possible to pick up unit-of -recovery information to resolve and complete all the work of the resource managers involved. If this is not possible, the indoubt units-of-recovery can be resolved using commands.
• Batch and non-message-driven BMPs in a DBCTL Environment

  Distributed Sync Point does not support the IMS batch environment. In a DBCTL environment, inbound protected conversations are not possible. However, a BMP in a DBCTL environment can allocate an outbound protected conversation, which will be supported by Distributed Sync Point and RRS.