SNAX/HLS Management Programming Manual

Standard SNAX/HLS Definitions
Common Definitions
104708 Tandem Computers Incorporated 6–13
ZCHAIN–PROTO
specifies the chaining protocol used by the half session. This is established by the
BIND record, and is one of the following enumerated values:
ZHLS–VAL–CHAIN–PROTO–ANY
specifies that both exception and definite response chains are used. This
protocol allows the message sender to choose whether to use definite or
exception response chains on a message–by–message basis. SNAX/HLS
interprets this protocol for the sender by selecting exception responses if no
notification is requested and definite responses if notification is requested.
ZHLS–VAL–CHAIN–PROTO–DEF
specifies that only definite response chains are used. This protocol specifically
asks for an acknowledgment for every complete message (chain) sent. This
means message delivery and acceptance can be known directly by the message
sender. Frequently, this is combined with immediate request mode and
SEND–DATA verb completions are delayed until the promised response
arrives.
ZHLS–VAL–CHAIN–PROTO–EXCPT
specifies that only exception response chains are used. This value corresponds
to requesting a response only in the event of failure. An application program
using this protocol must be able to accept the delayed receipt of a negative
response. This protocol minimizes SNA line overhead at the expense of
application logic.
ZHLS–VAL–CHAIN–PROTO–NONE
specifies that no responses are solicited by the requester. This value
corresponds to “datagram” delivery; that is, messages are sent without
acknowledgment of success or failure. This protocol has a minimal processing
overhead, but session partners must typically provide a higher–level
acknowledgment protocol to validate delivery and acceptance.
ZCHAIN–USE
specifies whether the half session sends single–RU or multiple–RU chains. This
value is set when the BIND message is processed. Chaining is enabled if the
ZHLS–VAL–CHAIN–USE–MULTI value is specified; otherwise, chaining is
disabled.
When chaining is enabled, SNAX/HLS breaks long application messages into
RU–sized units for transmission. Conversely, multiple–RU elements received are
recombined into complete messages. This facility can be overridden by use of the
large message option (LMO). For more information on the LMO, refer to the
SNAX/HLS Application Programming Manual and the SNAX/HLS Configuration and
Control Manual.