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Clear
If the 3708 disconnects its downstream device, the following actions occur:
• Devices connected to a nonswitched line return to the first 3708 screen (if 3708
logon screens are not excluded).
• Devices connected to a switched line are disconnected. The user must dial again
to gain access to the 3708.
If the 3708 does not disconnect its downstream device, the end user returns to the
3708's host selection screen (if the screen is not suppressed). Dial-up users are not
disconnected.
If logon screens are excluded and the downstream device is not disconnected (or no
host selection), the end user is returned to the SSCP-SLU session and may initiate
another session.
Options 4 and 5 are designed to be used with TSO, which transmits an
DACTLV/ACTLU sequence when the end user performs a normal logoff sequence.
If the 3708 logon screens are excluded, or the host selection screen is suppressed in
the 3708's configuration, the 3708 ignores any data input by the user between the
DACTLU and the proceeding ACTLV.
Session Security:
If the 3708 is configured to transmit an UNBIND for session
security, the 3708 transmits an UNBIND (OF) command to the host when users are
in session with their applications and power off their terminals or are abnormally
disconnected. The UNBIND (OF) ensures that the session is terminated by the
network and prevents another user from dialing in to the same 3708 port and
gaining access to a previous user's application.
Session security cannot be guaranteed by the 3708 if the host application maintains
resources over LU sessions or automatically reconnects the terminal when the
UNBIND (OF) or TERMSELF (40) is received.
When the 3708 receives a Clear command, it forces the data-traffic-reset state upon
the LV-LV session. Clear also causes the 3708 to initialize all inbound and
outbound transmission buffers. When data-traffic-reset state is activated for an
LV-LV session, only the following commands are valid for that session: VNBIND
and Start Data Traffic (SOT).
If
a SDT command is received, a second CLEAR command can be accepted. Two
CLEAR commands in a row will not be accepted and are rejected with a negative
sense code of X '2009
I •
Start Data Traffic (SDT)
This command allows FM data traffic to flow during an LU-LV session. The SDT
command must be issued after a BIND command has established the LV-LV
session.
It
is also sent after Clear to complete a session resynchronization sequence
with the 3708. SOT is valid only when the data-traffic-reset state is active for an
LV-LV session.
To complete a session resynchronization sequence, the host program must request
transmission of the SOT command from the access method.
Chapter 3. SDLC and SNA Communication
3-29
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