SNAX/HLS Configuration and Control Manual

Step 5. Planning for Programming Standards
Planning the SNAX/HLS Environment
2–24 104705 Tandem Computers Incorporated
An application program using SNAX/HLS, of course, does not directly see the failure
of either SNAX/XF or SNAX/CDF, or SNAX/HLS. Instead, SNAX/XF or
SNAX/CDF produces SNA sense-code errors for all subsequent data operations, and
SNAX/HLS produces a RETURN-CODE, RC-POSSIBLE-DATA-LOSS on all
session-oriented verbs until the session is deallocated.
The recovery from this situation is always to close the session with CLOSE-SESSION
or HLS-DEALLOCATE, and undertake application-level recovery. When relevant, a
judicious use of transaction protection and control greatly assists in this operation.
Step 5. Planning for
Programming
Standards
This subsection discusses the following programming practices recommended to
increase programmer productivity and to make application programs more reliable
and maintainable:
Use of standard copybooks
DATA-TYPE-RECEIVED indicator handling
Standard use of CONVERT-ERROR-CODE
Awareness of send/receive modes in HDX flows
SCOBOLX coding for SNAX/HLS LU names and SNAX/HLS server names
Use of Standard
Copybooks
SNAX/HLS provides a copybook for SCOBOLX programs (source module HLSDDS)
and one for TAL programs (source module HLSDDT). In a format suitable for the
language, each contains definitions of the code values and data structures used to
communicate with the SNAX/HLS server along with textual equivalents of the code
values. Details on how to use the copybooks are discussed in the SNAX/HLS
Application Programming Manual. Their use within application programs promotes
uniformity of naming.
DATA-TYPE-RECEIVED
Indicator
The SNAX/HLS server stores messages for the application in the session’s receive
queue to be delivered in response to a receive verb. The completion of the verb,
however, does not necessarily deliver a message from the session partner because
several other possible messages can complete this verb. The message might, for
example, be an interrupt message from the operator or a status message from the
session partner.
It is recommended that the completion of RECEIVE-DATA or
SEND-AND-RECEIVE-DATA verbs be accomplished using a standard procedure or
paragraph that implements the following pseudocode, that is similar to TAL.