This section describes the commit protocols that flow between APPC systems during a syncpoint. The arrows in the diagrams show the syncpoint flows in more detail than in the figures earlier in this section.
First, consider a simple distributed process involving only one conversation, as in Figure 43. Here is what happens:
When the syncpoint agent has a conversation with a third transaction, Figure 44 shows the flows that occur. Here is what happens:
When the syncpoint initiator has two concurrent conversations, the flows involved are shown in Figure 45. Here is what happens:
If the syncpoint initiator decides to prepare the conversation with system 2 explicitly before issuing a syncpoint, the flows involved are shown in Figure 46. In this case, the application program in system 1 issues an ISSUE PREPARE command, followed by SYNCPOINT command, rather than just a SYNCPOINT command; however, the flows across the links are exactly the same as those in the previous example. Using the ISSUE PREPARE command gives the application the opportunity to "change its mind" and rollback, depending on the response to ISSUE PREPARE.
For further information on the flows in a distributed process, see the SNA Reference: Peer Protocols book.
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