HP-UX SNAplus2 R7 LUA Programmer's Guide

Designing and Writing LUA Applications
SNA Information
Distinguishing SNA Sense Codes from Other Secondary Return Codes
Note
The byte ordering used in LUA secondary return codes means that the most significant byte
of the numeric value is the last byte, not the first byte.
For a secondary return code that is not a sense code, the two most significant bytes of this value are always
0
(zero). As an example,
0x01000000 (LUA_INVALID_LUNAME) is a standard LUA secondary return code and
not a sense code.
For an SNA sense code, the two most significant bytes are nonzero; the most significant byte gives the sense code
category, and the next byte identifies a particular sense code within that category. (The remaining bytes may contain
additional information, or may be
0.) As an example, 0x00000108 (LUA_RESOURCE_NOT_AVAILABLE)isa
sense code.
All LUA secondary return codes, including those that are SNA sense codes, are listed in Appendix A,
Return Code
Values.
Information about SNA Sense Codes
If you need information about a returned sense code, refer to IBM’s Systems Network Architecture: Formats. The
sense codes are listed in numerical order by category.
2.4.4 Pacing
Pacing is handled by the LUA interface; an LUA application does not need to control pacing, and should never set
the Pacing Indicator flag.
If pacing is being used on data sent from the LUA application to the host (this is determined by the BIND), an
RUI_WRITE or SLI_SEND verb may take some time to complete. This is because SNAplus2 has to wait for a
pacing response from the host before it can send more data.
If an LUA application is used to transfer large quantities of data in one direction, either to the host or from the host
(for example, a file transfer application), then the host configuration should specify that pacing is used in that direc-
tion; this is to ensure that the node receiving the data is not flooded with data and does not run out of data storage.
2.4.5 Segmentation
Segmentation of RUs is handled by the LUA interface. LUA always passes complete RUs to the application, and
the application should pass complete RUs to LUA.
2.4.6 Modification of Nonstandard Host Response/Request Header
(RH) Bits
A host may send data to an LUA application with the BB (begin bracket) and RQE (request exception) options
set but without the EB (end bracket) option (begin bracket and exception response but no end bracket). This
combination of options is not strictly valid in SNA, but is used by some host applications.
In order to support these host applications, SNAplus2 modifies the host data to specify definite response rather than
exception response before sending it to the application.
2.4.7 Courtesy Acknowledgments
SNAplus2 keeps a record of requests received from the host in order to correlate any response sent by the application
with the appropriate request. When the application sends a response, SNAplus2 correlates this with the data from
the original request, and can then free the storage associated with it.
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