SNAX/CNM Manual

INTRODUCTION
Additional Buffer Parameters
ADDITIONAL BUFFER PARAMETERS
Some verbs require that additional parameters be appended to the
verb/reply header. These additional parameters are explained in
Section 2, "Verb Directory." For all verbs, a negative reply
leaves these additional parameters unchanged.
For the cases where you must provide an SNA record in a verb,
you must reserve space for a 6-byte TH header, but the value you
include is overridden by SNAX. The recommended TH is 0.
For most verbs, a positive reply causes additional information
to be appended to the verb/reply header. The format of this
information is given in Section 3, "Reply Directory."
ERROR HANDLING
Your program should be constructed to deal with the following
three types of errors:
• File-system errors. These errors are signaled by a nonzero
condition code immediately after an AWAITIO. Your program can
call FILEINFO to get the error code, as is the normal practice
in file-system operations.
• Errors reported in a negative CNM reply. Assuming that an
AWAITIO completes with no indication of error, a negative
reply in the READ part of a WRITEREAD signals an error in the
verb. For example, the verb may have asked for information
about a nonexisting device. When your program receives a
negative reply, it should examine the Internal Error and the
External Error fields of the negative reply.
• SNA errors. For verbs directed to the CNM component of $SSCP,
a positive reply does not guarantee the absence of errors.
When your program receives a positive reply, it should examine
the REQMS record, the RECFMS record or the NMVT in the reply
to detect a possible SNA negative response.
1-10