CICS ONC RPC control flow

Figure 36 shows the components involved in processing a typical client ONC RPC request.

Figure 36. Call processing
 This diagram shows the steps described in the following text.

Client requests are processed in the following steps:

  1. A request from a client arrives in TCP/IP for MVS™.
  2. The server controller monitors the TCP/IP for MVS interface for incoming client requests, and the client request is passed to it. (From the 4-tuple for the request, the server controller can find the corresponding XDR routine and converter to call.)
  3. The server controller invokes the inbound XDR routine.
  4. The server controller calls the converter, requesting the Decode function, if it is required for the 4-tuple. If Decode is not required, the server controller allocates storage for the CICS® program communication area.
  5. The server controller then starts an alias to deal with all further processing of the request within CICS.
  6. The server controller returns to monitor the TCP/IP for MVS interface for client requests.
  7. The alias optionally calls a user-written resource checker.
  8. The alias issues an EXEC CICS LINK to the CICS program for the 4-tuple. The communication area set up by Decode is passed in the LINK command.
  9. The CICS program processes the request and returns its output to the alias program in the communication area.
  10. The alias calls the Encode function, if it is required for the 4-tuple.
  11. The alias invokes the outbound XDR routine.
  12. The alias returns the reply to TCP/IP for MVS, and ends.
  13. The reply is sent back to the client.

Updating recoverable resources

After Decode processing, the server controller uses EXEC CICS SYNCPOINT to commit any changes to recoverable resources that Decode might have made.

If the CICS program makes updates to recoverable resources, whether the changes are committed or backed out depends on the location of the CICS program, and on whether it uses the EXEC CICS SYNCPOINT command.

Related concepts
ONC RPC concepts
ONC RPC remote procedures and CICS programs
CICS ONC RPC transactions
CICS ONC RPC user-replaceable programs
CICS ONC RPC data flow
Related tasks
Setting up CICS ONC RPC
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