SNAX/APN Application Programming Manual

The SNALU Interface
SNAX/APN Application Programming Manual—420111-001
4-14
Remote SLU Initiates Session With SNALU
Application
For negative responses, the SNALU application should at least examine the sense data
(bytes 9 through 12 of the incoming record) to determine why the SLU responded
negatively. As with positive responses, it may also want to check the request code and
sequence number to verify which request is being responded to.
Bytes 9 through 12 of a negative response contain a 4-byte SNA sense code that
specifies why the request was rejected. The sense codes are summarized in Appendix B
of this manual and described in greater detail in the IBM Systems Network Architecture:
Network Product Formats manual.
Remote SLU Initiates Session With SNALU Application
When the SNALU application is the PLU, it may sometimes be desirable to open the
remote LU, issue a read request, and wait for a CINIT request before establishing the
session with an SLU. This is called PLU Accept Mode.
If the SLU is a device, the logon information can be either
•
entered by an operator through the device’s keyboard (character-coded logon) or
•
generated automatically (perhaps initiated by time of day) by the device’s microcode
(INIT-SELF request).
If the SLU is an application process, the logon information consists of either an INIT-
SELF request or a character-coded logon request.
The logon information is forwarded to the Tandem application in a CINIT request. The
Tandem application then issues a BIND request. For illustrations of situations in which
PLU Accept is used, see Appendix C, Logic Flows and Internal Formats When Using
SNALU.
The IBM Systems Network Architecture: Format and Protocol Reference: Architectural
Logic shows the format of the CINIT request. Note that the CINIT that appears in the
application’s buffer has a session-key value of X '15'.
Upon receipt of the CINIT request, the SNALU application can send a positive response
and then initiates the session as described previously. The SNALU application must
send a positive or negative response in reply to a CINIT request.
SNALU Application Initiates Session With Remote PLU
When the SNALU application is the SLU, it can solicit a BIND request from the PLU
by sending an INIT-SELF request or a character-coded logon request. This is called
9-12 sense data
13 request code (X’31’ for BIND)
Table 4-3. Negative Response to BIND Request (page 2 of 2)
Byte Description