When a logical unit requests a session with an application program,
it uses a symbolic logon mode name, either directly or by default,
to suggest the session protocols. Session protocols are a set of rules
that describe how the session is conducted. For example, one protocol
might specify the application program uses chaining for SNA requests.
Another might require the logical unit does not send end-bracket indicators
to the application program. For a complete description of the session
protocols available in VTAM®, see z/OS Communications Server: SNA Programming.
Session protocols are expressed as a string of characters called
session parameters, usually specified in the logon mode table. A set
of session parameters for a session is also called its logon mode. VTAM contains an IBM-supplied logon
mode table, ISTINCLM. This table contains a set of generally accepted
session parameters for a basic list of IBM® device types, but it might not completely meet your needs.
You can create supplementary logon mode tables and associate them
with device type logical units or application programs using the MODETAB
operands on the definition statements defining them.
To create the logon mode table:
- Modify the IBM-supplied table.
- Create supplementary tables and associate them with device-type
LUs or application programs using the MODETAB operands in the definition
statements defining them. You can use the DLOGMOD operand on the appropriate
definition statements to indicate the specific logon mode entry in
the table that contains the session parameters to be used by default.
The LOGMODE operand can also be specified on VARY LOGON commands to
specify a logon mode table entry.
- Associate a supplementary table with dynamic CDRSCs using the
DYNMODTB start option. You can also use the DYNDLGMD start option to indicate
the default logon mode entry for dynamic CDRSCs. The value for DYNMODTB
can be changed using the DYNMODTB operand on the MODIFY VTAMOPTS command,
or by using the MODIFY TABLE,OPTION=LOAD command to replace the existing
table that is being used by dynamic CDRSCs. You can change the default
logon mode entry for dynamic CDRSCs using the DYNDLGMD operand on
the MODIFY VTAMOPTS command. You can also override this value for
a specific dynamic CDRSC using the MODIFY DEFAULTS or MODIFY RESOURCE
commands.
When VTAM builds
a dynamic CDRSC, it uses the DYNMODTB value (if specified; otherwise
ISTINCLM) to associate a logon mode table to the dynamic CDRSC. It
also uses the DYNLOGMD value, if specified, to assign a default logon
mode table entry to the dynamic CDRSC. Changing the value of these
start options does not change the value for dynamic CDRSCs that have
already been built.
Logon mode names are always resolved using the logon mode table
associated with the secondary logical unit (SLU). For more information
about which node performs the mode resolution, see Resolving logon mode names to subarea and APPN Classes of Service.
Logon mode tables are created or modified using MODETAB, MODEENT,
and MODEEND macro instructions. The z/OS Communications Server: SNA Resource Definition
Reference describes the contents of the IBM-supplied
logon mode table. It also describes how TSO can query for the logon
mode being used by a terminal in place of supplying the LOGMODE during
the logon. Figure 1 shows the sequence
in which MODETAB, MODEENT, and MODEEND macros are coded to define
a logon mode table.
Figure 1. Macroinstructions for logon mode table
The various ways of specifying session parameters are illustrated
in Table 1.
Table 1. How session parameters
are identifiedRequest source |
Request form |
How
session parameters are identified |
---|
Logon mode table entry |
Logon mode table |
---|
Dependent Logical Unit |
- Initiated Self request
- Interpret table character string representing logon
- Character-coded logon
|
- Field in Initiate Self request containing mode name used to search
logon mode table
- Parameter in a character-coded logon that translates into LOGMODE
(name)
- DLOGMOD operand on LU definition statement
- Default entry ISTCOSDF, if the ISTCOSDF start option allows its
use for dependent LUs
- First entry in logon mode table named in MODETAB operand on LU
definition statement
- First entry in IBM-supplied logon mode table
|
- MODETAB operand on LU definition statement
- IBM-supplied logon mode table
|
Independent Logical Unit |
- BIND
- Cross-domain initiate
|
- Field in BIND or cross-domain initiate request containing mode
name used to search logon mode table
- DLOGMOD operand on CDRSC definition statement, or DYNDLGMD start
option value (for dynamic CDRSCs)
- Default entry ISTCOSDF, if the ISTCOSDF start option allows its
use for independent LUs
- First entry in logon mode table named in MODETAB operand on CDRSC
definition statement or DYNMODTB start option value (for dynamic CDRSCs)
- First entry in IBM-supplied logon mode table
|
- MODETAB operand on CDRSC definition statement or DYNMODTB start
option value (for dynamic CDRSCs)
- IBM-supplied logon mode table
|
Application Program |
Application program issuing VTAM macros,
such as SIMLOGON or REQSESS |
- Name of logon mode table entry specified in the NIB
- DLOGMOD operand on LU definition statement
- Default entry ISTCOSDF, if the ISTCOSDF start option allows its
use for application programs
- First entry in logon mode table named in MODETAB operand on LU
definition statement
- First entry in IBM-supplied logon mode table
|
|
Automatic logon |
Initiate® Other request |
- DLOGMOD operand on LU or CDRSC definition statement or DYNDLGMD
start option value for dynamic CDRSCs
- Default entry ISTCOSDF, if the ISTCOSDF start option allows its
use
- First entry in logon mode table named in MODETAB operand on LU
or CDRSC definition statement, or DYNMODTB start option value for
dynamic CDRSC
- First entry in IBM-supplied logon mode table
|
|
VTAM operator |
VARY LOGON command |
- LOGMODE operand in VARY LOGON command
- LOGMODE operand in previous VARY LOGON command
- DLOGMOD operand on LU or CDRSC definition statement, or DYNDLGMD
start option value for dynamic CDRSCs
- Default entry ISTCOSDF, if the ISTCOSDF start option allows its
use
- First entry in logon mode table named in MODETAB operand on LU
or CDRSC definition statement, or DYNDLGMD start option value for
dynamic CDRSCs
- First entry in IBM-supplied logon mode table
|
|
Regardless of the source of the logon or what session parameters
are associated with the logon, the application program decides which
session parameters are used for the session. It can decide to use
the session parameters associated with the pending logon, or it can
choose a different set of parameters. When the application program
issues a macro to initiate a session with a logical unit, the application
program indicates the logon mode name or session parameters to be
used during the session. The logon mode table from which the session
parameters are selected is always the one associated with the SLU,
or, if a table is not associated with the logical unit, it is the
IBM-supplied default logon mode table in the VTAM that owns the SLU.
If the specified logon mode entry does not exist in the logon mode
table associated with the secondary logical unit, the default logon
mode (ISTCOSDF) is used if it is found
in the table and its use is allowed as determined by the ISTCOSDF
start option.
You can modify or replace the IBM-supplied logon mode table, provided
that the modified or replacement table has the same name as the IBM-supplied
table and that the IBM-supplied table is deleted. However, because
the IBM-supplied table might be needed for problem determination,
you should create supplementary tables instead of deleting the IBM-supplied
table.
As part of the session-establishment procedures, an application
program acting as the PLU can:
- Supply a logon mode name associated with the SLU. The session
parameters associated with the logon mode name in the domain of the
SLU are used.
- Directly supply the session parameters to be used.
- Use the session parameters associated with the pending logon.
z/OS Communications Server: SNA Programming describes in more detail how the application
program handles session parameters.
Figure 2 shows a summary of the algorithm VTAM uses to obtain session parameters.
Figure 2. How session parameters are obtained from
a logon mode table