Distributed sync point

The Distributed Sync Point support enables IMS and remote application programs (APPC or OTMA) to participate in protected conversations with coordinated resource updates and recoveries. Before this support, IMS acted as the sync-point manager. In this new scenario, z/OS® manages the sync-point process on behalf of the conversation participants: the application program and IMS (now acting as a resource manager).

z/OS implements a system resource recovery platform, the z/OS Resource Recovery Services (RRS). RRS supports the Common Programming Interface - Resource Recovery (CPI-RR), an element of the SAA Common Programming Interface that defines resource recovery and provides for the coordinated management of resource recovery for both local and distributed resources. In addition to RRS, a communications resource manager (called APPC/PC for APPC/Protected Conversations) provides distribution of the recovery.

In the APPC environment, a protected conversation is initiated when the application program allocates an APPC conversation with SYNC_LEVEL=SYNCPT. Both IMS and APPC are resource managers in this scenario. In the OTMA environment, some additional code is required because OTMA is not a resource manager. The additional code needed is an OTMA adapter, IBM® supplied or equivalent. This adapter indicates to IMS (in the OTMA message prefix) that this message is part of a protected conversation, and thus IMS and the adapter are participants in the coordinated commit process as managed by RRS.

Application programmers can now develop APPC application programs (local and remote) and remote OTMA application programs that use RRS as the sync-point manager, rather than IMS. This enhancement enables resources across multiple platforms to be updated and recovered in a coordinated manner.

Distributed sync point concepts

The Distributed Sync Point support entails:

  • Changes in IMS that allow it to function as a resource manager under RRS
  • Changes to the application program environment that support using applications in protected conversations
  • Changes to some commands that aid the user

Impact on the network

Network traffic will increase as a result of the conversation participants and the sync-point manager communicating with each other.