SNAX/HLS Configuration and Control Manual

Step 4. Planning the Application Environment
Planning the SNAX/HLS Environment
104705 Tandem Computers Incorporated 2–23
Accept Bind
When your application is acting as the primary LU, you can elect to establish sessions
either by acquisition (your side issues the BIND unilaterally) or by acceptance (your
side waits for a CINIT message and then issues the BIND). In the latter case, the
Tandem SNA access method SNAX/CDF supplies a suggested BIND image in the text
of the CINIT message. SNAX/HLS can be directed to accept the suggested BIND
image or to override it with one of your choosing. The ACCEPT BIND PROFILE
attribute specifies the choice.
Note The Tandem SNA access method SNAX/XF does not supply a BIND image in the CINIT. This PROFILE
attribute should only be set if SNAX/HLS is being used in conjunction with SNAX/CDF.
If you select ACCEPT-BIND set to YES, you should be aware that your session will be
established with BIND parameters over which you have little direct control.
Request Send State
SNAX/HLS provides the PROFILE attribute FORCE-RTS to control the operation of
the REQUEST-SEND-STATE verb. If the attribute is not set, the verb only causes a
SNA SIG request to be sent if the local session partner does not 'currently' have the
right to send on the normal SNA flow. If the attribute is set, the SNA SIG request is
sent whenever the REQUEST–SEND–STATE verb is issued, regardless of the states of
the normal SNA session.
NonStop Programming
Considerations
You should carefully consider the development of an application as a NonStop process
pair. High-availability environments can be built only through careful application
design.
The SNAX/HLS backup process assumes control if the primary copy fails for any
reason. The unexpected failures can originate from a software failure, a CPU failure,
or some catastrophic event sensed within SNAX/HLS itself. Planned failures can
originate from a STOP command directed to the primary process, the ABEND
command of HLSCOM, or the SWITCH PROCESS programmatic command.
The SNAX/XF line or SNAX/CDF process similarly assumes control if the primary
copy fails for any reason. The reasons are similar.
You should note two critical facts:
The SNAX/XF or SNAX/CDF product does not checkpoint the data entrusted to
its care for transmission (send or receive). Therefore, if the backup assumes
processing, all sessions on the affected lines are no longer valid.
SNAX/HLS does not checkpoint the data entrusted to its care for transmission
(send or receive). Therefore, if a SNAX/HLS backup assumes processing, all
sessions it was managing are no longer valid.