To help you understand the process, consider what takes place when you
log on to CICS® through
VTAM. (The process is illustrated in
Figure 1 and
Figure 2.) CICS supports the model terminal
support (MTS) function of VTAM 3.3 and above. Using MTS, you can define the
model name, the printer (PRINTER), and the alternate printer (ALTPRINTER)
for each terminal in a VTAM table. CICS captures this information as part
of autoinstall processing at logon, and uses it to create a TCTTE for the
terminal. If you are using MTS, you must use a version of DFHZATDX that is
suitable for use on
CICS Transaction Server for z/OS®.
See
CICS Customization
Guide for programming information about the user-replaceable autoinstall
program.
- VTAM receives your request, determines that you want to use CICS, and
passes your request to CICS.
- CICS extracts your terminal's NETNAME name from the logon data. CICS searches
the TCT for an entry with the same NETNAME.
- If it finds such an entry, CICS issues an OPNDST to VTAM to establish
a session between CICS and the terminal. This is the normal CICS logon process.
- If it fails to find a matching entry, CICS checks the system initialization
parameters that were specified in the SIT, or reset using CEMT, to check whether
it can allow an autoinstall.
- If the system initialization parameters allow an autoinstall, CICS checks
the terminal data passed by VTAM, to check whether the terminal is eligible
for autoinstall.
- If the terminal is eligible, CICS examines the bind image to see if it
carries sufficient information.
- If the VTAM bind image data proves sufficient, CICS searches the autoinstall
model table (AMT) in sorted ascending order, and autoinstalls the terminal
in one of the following ways:
- If VTAM has supplied CICS with a valid model name, CICS passes this name
to the autoinstall control program. (If the logon request has come
to CICS through VTAM 3.3, and if you have supplied VTAM with names of model
terminals, CICS can obtain the name of the model terminal from the logon data.)
- If VTAM has not supplied CICS with a valid model name, CICS searches the
AMT for suitable autoinstall models and passes these to an autoinstall control
program, together with VTAM logon data. If VTAM has supplied CICS with
an invalid model name, message DFHZC6936 results.
- The autoinstall control program (either the CICS-supplied program or one
written by you) selects one of the models and provides the rest of the information
necessary to complete a TCT entry for the terminal.
- When the autoinstall control program returns control, CICS builds a TCT
entry using the autoinstall model, the data returned by the autoinstall control
program, and the VTAM logon data for the terminal. CICS then adds the new
entry to the TCT and issues an OPNDST to VTAM to establish a session between
CICS and the terminal.
- If the TYPETERM definition so specifies, CICS uses
the QUERY function to find out about some of the features of the terminal.
(These features are listed in TYPETERM resource definitions.)
Figure 1. The process of logging on to CICS
using autoinstall.
Note that the autoinstall process itself
is shown as a single box. What happens inside this box is depicted in Figure 2
Figure 2. How CICS autoinstalls
a terminal.
Note that the overall process in which this fits
is shown in Figure 1
.