gtpm3m0g | Multi-Processor Interconnect Facility Reference |
Figure 3 and Figure 4 describe the MPIF macro flows and the use of tokens and user exits. Tokens are shown as TKnn. The user exits are indicated as:
CCX - Connection completion exit
CRX - Connection request exit
DRX - Data receive exit
ERX - Error exit.
Figure 3 shows an example of the flow for IDENTIFY/CONNECT and indicates three possible responses to CONNECT:
Figure 3. MPIF IDENTIFY and CONNECT Flows
Also, a connect race condition can occur if both X and Y issue CONNECT at the same time; only one connection is needed. MPIF supports n connections between users. If users desire only one, they must define a startup protocol to determine which user can issue the connection.
All events associated with establishing a connection occur across the path allocated to the originating CONNECT request. This simplifies processing for path failures. If a path fails during this processing, the connect request is failed. This avoids having to recover from all the conditions that a path failure can produce, including receiving obsolete requests about a connection.
Figure 4 shows an example of the flow for SEND/DISCONNECT.
Figure 4. MPIF SEND and DISCONNECT Flows
In Figure 3 and Figure 4 the fact that the user in X issued a SEND first is just for example. The user in Y can issue a SEND first, but this might result in X receiving a message before being told that the connection is complete.