Confirmation Processing
The sequence of events for confirmation processing is as follows:
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Establish the synchronization level.
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Send a confirmation request.
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Receive data and confirmation request.
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Respond to the confirmation request.
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Deallocate the conversation.
Using confirmation processing, a TP sends a confirmation request with the data; the partner TP confirms receipt of the data or indicates that an error occurred. Each time the two TPs exchange a confirmation request and response, they are synchronized.
Note Although the example in this section does not show this, any TP can send or receive data, regardless of whether the TP is the invoking TP or the invokable TP.
The following example illustrates confirmation processing.
| Issued by the invoking TP |
Issued by the invokable TP |
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TP_STARTED
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MC_ALLOCATE
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(synclevel=AP_CONFIRM_SYNC_LEVEL)
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MC_SEND_DATA
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(type=AP_SEND_DATA_CONFIRM)
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RECEIVE_ALLOCATE
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MC_RECEIVE_AND_WAIT
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(primary_rc=AP_OK)
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(rtn_status=AP_YES)
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(what_rcvd=
AP_DATA_COMPLETE_CONFIRM)
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MC_CONFIRMED
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MC_SEND_DATA
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(type=AP_SEND_DATA_DEALLOC_SYNC_LEVEL)
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MC_RECEIVE_AND_WAIT
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(primary_rc=AP_OK)
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(rtn_status=AP_YES)
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(what_rcvd=
AP_DATA_COMPLETE_CONFIRM_
DEALLOCATE)
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MC_CONFIRMED
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TP_ENDED
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TP_ENDED
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Establishing the Synchronization Level
The synclevel parameter of MC_ALLOCATE determines the synchronization level of the conversation. There are three possible synchronization levels:
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AP_NONE, under which confirmation processing does not occur.
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AP_CONFIRM_SYNC_LEVEL, under which the TPs can request confirmation of receipt of data and respond to requests for confirmation of data.
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AP_SYNCPT, under which the TPs operate under Sync Point Level 2 support for confirmation of receipt of data.
Sending a Confirmation Request
MC_SEND_DATA with type AP_SEND_DATA_CONFIRM has two effects:
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It flushes the local LU's send buffer and sends any data contained in the buffer to the partner TP.
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It sends a confirmation request that the partner TP receives through the what_rcvd parameter of a receive verb.
After issuing MC_SEND_DATA, the local TP waits for confirmation from the partner TP.
Receiving Data and Confirmation Request
The what_rcvd parameter of MC_RECEIVE_AND_WAIT indicates:
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Status of the data received: complete or incomplete.
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Future processing expected of the local TP.
In the example, what_rcvd is ap_data_complete_confirm, indicating that the status is complete and a confirmation is requested.
Responding to a Confirmation Request
The partner TP issues MC_CONFIRMED to confirm receipt of data. This frees the local TP to resume processing.
Deallocating the Conversation
MC_SEND_DATA sends a confirmation request with the data when all of the following conditions are true:
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The conversation's synchronization level (established by the synclevel parameter of MC_ALLOCATE) is AP_CONFIRM_SYNC_LEVEL.
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The type parameter of MC_SEND_DATA is set to AP_SEND_DATA_DEALLOC_SYNC_LEVEL.
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The what_rcvd parameter of the final MC_RECEIVE_AND_WAIT is AP_DATA_COMPLETE_CONFIRM_DEALLOCATE, indicating that a confirmation of receipt of data is required before APPC will deallocate the conversation. The local TP waits for this confirmation until the partner TP issues MC_CONFIRMED.