TN3270E connections require an Early Lookup during connection negotiation.
Telnet will use as much information as is available to assign an
LU to the client. However, the eventual application is not known
at this time unless an LUMAP-DEFAPPL or DEFAULTAPPL statement defines
the application name. After connection negotiations are complete,
Telnet will either send a logon solicitor (or USSMSG10) screen to
the client or will perform a Complete Lookup using the application
name obtained from the LUMAP-DEFAPPL or DEFAULTAPPL statement. If
Complete Lookup is successful, Telnet will begin session initiation.
If a solicitor (or USSMSG10) screen is sent to the client, an application
name must be entered, at which time Telnet will perform a Complete
Lookup. If LU mapping is being done based on application name, a conflict
might occur between the application LU mapping and the LU already
assigned to the connection. For TN3270E, after an LU name is assigned
during connection negotiation it can never change until the connection
is dropped. The SIMCLIENTLU statement allows Telnet to assign LUs
for TN3270E connections as though they were TN3270 connections. See TN3270 LU mapping for mapping
Generic TN3270E connection requests with SIMCLIENTLU. A request for
a Specific LU from the Telnet Client will be treated as if SIMCLIENTLU
were not specified. The exact lookup process for TN3270E (non-SIMCLIENTLU)
is described below.
Early Lookup: An LU must be found during Early Lookup. LUMAP-DEFAPPL
and DEFAULTAPPL statements are considered but not necessarily used.
Possible lookup results are:
- An LU is found.
- An LU is not found, the connection is dropped.
Perform TN3270E Early Lookup in the following order. The process
stops when LU lookup is successful. Printer connections use the same
process, substituting PRTMAP and PRTDEFAULTAPPL.
- Check for LUMAP matches considering application lookup results
and possible application-based LU mappings.
- For each Specific LUMAP used for Specific connection requests:
If the Specific LUMAP has DEFAPPL, or DEFAULTAPPL was specified and
the application lookup return code is either OK or USER_REQUIRED,
then perform LU lookup.
- For each Generic LUMAP used for Specific or Generic connection
requests: If the Generic LUMAP has DEFAPPL, or DEFAULTAPPL was specified
and the application lookup return code is either OK or USER_REQUIRED,
then perform LU lookup.
- Check for LUMAP matches without considering application lookup
results.
- For each Specific LUMAP used for Specific connection requests:
Ignore DEFAPPL and DEFAULTAPPL and perform LU lookup.
- For each Generic LUMAP used for Specific and Generic connection
requests: Ignore DEFAPPL and DEFAULTAPPL and perform LU lookup.
- If LUMAP statements were not checked (different from checked but
no match), use the appropriate Default LU pool considering application
lookup results and possible application-based LU mappings. In this
case the only relevant application is the DEFAULTAPPL, if specified.
If the application lookup return code is either OK or USER_REQUIRED,
then perform LU lookup.
- If LUMAP statements were not checked, try the appropriate Default
LU pool without considering application lookup results. Perform LU
lookup.
Complete Lookup: An application name is required for Complete Lookup.
The application name is obtained from one of three sources in the
order specified.
- Input from the USER or VTAM® (via
CLSDST with OPTCD=PASS)
- DEFAPPL parameter on the LUMAP statement
- DEFAULTAPPL statement
Use the application name and the previously found LU to perform
Complete Lookup.
Possible lookup results are:
- The application is not valid.
- The application is valid (return code OK or USER_REQUIRED) for
the existing LU.
- The application-based LU map does not match the already chosen
LU.