SNAX/HLS Configuration and Control Manual

Step 3. Planning Session BINDs
Planning the SNAX/HLS Environment
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SNAX/CDF completes, not when the session partner acknowledges the message.
In this case, completion of the verb cannot be construed as the session partner’s
acceptance of the message. SNAX/HLS applications must contain logic to handle
situations where the completion of a SEND verb is followed later by a
RC-REQUEST-REJECT return code on the receive queue regarding a previous
message.
Immediate-request mode —allows only one message requesting explicit
acknowledgement to be outstanding. If a SNAX/HLS application sends a
message requesting a response, the verb completes when the explicit
acknowledgement arrives, and the SNAX/HLS application can assume that the
session partner accepted the message. Note that for this condition to hold, either
definite-response mode or definite or exception mode must be specified, and the
SEND verb must ask for notification. If the response protocol is no response (that
is, datagram service) or exception response (that is, notification of errors only),
SEND verbs complete when the I/O to SNAX/XF or SNAX/CDF completes.
In the BIND message, this attribute is indicated in byte 4, bit 1, for the primary half-
session, and in byte 5, bit 1, for the secondary half-session. In HLSRDT, this option is
specified by the BIND attributes PRI-CHAIN-PROTOCOL and SEC-CHAIN-
PROTOCOL, respectively.
Chain Response Protocol
This attribute specifies what types of responses can be solicited on function
management data (FMD) requests.
No-response chains —allow datagram service messages to be sent without
acknowledgement of success or failure. This provides minimum
message-processing overhead, but session partners must use a higher-level
protocol to validate message arrival or acceptance.
Exception-response chains —allow message-delivery failures and session-partner
rejections to be returned to the message sender, but explicit acknowledgements
cannot be requested. SEND verbs complete on SNAX/XF or SNAX/CDF I/O
completions. An application must be able to handle conditions of later rejection by
a session partner. This minimizes SNA line overhead at the expense of application
logic.