IBM 3708 Description page 81

An LU-LU session is started by the host application program when it issues the
BIND request. The LU-LU session may be initiated by the host application
program (for example, acquiring the terminal or by a simulated logon) or by the
display terminal operator
#7 (a character-coded logon). If a character-coded logon
is received by the access method, the SSCP translates the logon request and
schedules a logon exit #8 for the PLU. After the PLU receives control at the logon
exit, or when the PLU acquires the terminal, the PLU passes an open session request
to the SSCP #9 which results in an SNA BIND #lEI being passed to the 3708 SLU.
The 3708 examines the session parameters of the BIND and, if they are acceptable,
allows the session to be established by sending a positive response to the BIND
command. See "BIND Check" on page 3-24 to verify acceptable session
parameters. If the session parameters are not acceptable, the 3708 rejects the BIND
command by returning a negative response (X'0821'), indicating that the session
parameters are invalid.
Once accepted, the BIND determines the basic LU-LU session characteristics (LU
type 1, LU type 2, or LU type 3). The 3708 also uses the device type defined in its
configuration to distinguish between the two LU 1 types (LU type 1 SCS and LU
type 1 NTO).
After the BIND command has been accepted with a positive response, the host
program can issue the Start Data Traffic command #11 to allow data traffic to flow
for the session.
Terminating an LU-LU Session
LU-LU sessions can be terminated in the following ways:
• The PLU can terminate an LU-LU session by requesting that the SSCP close the
session. The SSCP then sends an UNBIND command to the 3708 SLU. The
UNBIND terminates the LU-LU session.
• LU type 2 sessions can be terminated by the display operator in two ways:
1. The display operator may inform the PLU, for example, by a logoff request
(on the LU-LU session), that termination is desired. The PLU then
terminates the session by transmitting an UNBIND command.
2. The display operator changes from an LU-LU session to an SSCP-SLU
session by using the System Request key sequence and enters a logoff
message. If the logoff message is conditional, the SSCP passes the logoff
request to the PLU. If the logoff message is unconditional, the SSCP
transmits an UNBIND command to the 3708 SLU.
• LU type 1 NTO users may log off their applications by issuing a system request
simulation string followed by their application's logoff sequence. These strings
are defined in the 3708 configuration (the default is 99999).
• A PLU may close the session in an orderly fashion by issuing a Shutdown
command. When the host program issues the Shutdown command, the 3708
returns the Shutdown Complete command after completing any outstanding
operation and entering the Between
Brack~t
state. The PLU must close a
bracket with end bracket before the Shutdown command is effective.
• If an ACTLU (Cold) command is received from the SSCP while an LU-LU
session exists, the 3708 terminates the LU-LU session and reset the SSCP-LU
session. (ACTLU (ERP) commands do not terminate the LU-LU session.)
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IBM 3708 Description