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Terminal identifiers
The terminal identifier (TERMID) passed to the CICS autoinstall function at install of
a virtual terminal is determined using the following sequence:
1. For EPI programs:From the NetName parameter of the
CICS_EpiAddTerminal function, if specified by the Client EPI program.
For the Client terminal emulator:From the /n parameter of the cicsterm
command used to start the emulator, if specified by the workstation user.
2. A name generated automatically by CICS.
TERMIDs generated by CICS for Client terminals consist of a 1-character prefix
and a 3-character suffix. The default prefix is '\', but you can specify a different
prefix using the VTPREFIX system initialization parameter. The suffix can have
the values 'AAA' through '999'. That is, each character in the suffix can have the
value 'A' through 'Z' or '0' through '9'. The first suffix generated by CICS has the
value 'AAA'. This is followed by 'AAB', 'AAC', ... 'AAZ', 'AA0', 'AA1', and so on,
up to '999'.
Each time a Client virtual terminal is autoinstalled, CICS generates a
3-character suffix that it has not recorded as being in use.
Note: By specifying a prefix, you can ensure that the TERMIDs of Client
terminals autoinstalled on this system are unique in your transaction
routing network. This prevents the conflicts that could occur if two or
more regions ship definitions of virtual terminals to the same
application-owning region (AOR).
For details of the VTPREFIX system initialization parameter, see the
CICS
System Definition Guide
.
For brevity, we shall refer to the name specified by the Client or the
CICS-generated “VTPREFIX” name as the
supplied name
. The Client always knows
the virtual terminal by the supplied name. However, your autoinstall control program
can allocate an alias, by which the virtual terminal will be known to CICS.
If the CICS autoinstall function detects that the supplied name clashes with the
name of a remote terminal or connection already installed on this region, it
generates an alias TERMID. CICS generates alias TERMIDs for virtual terminals in
the same way as it generates aliases for shipped terminals—see “CICS-generated
aliases” on page 524.
Note: If the supplied name clashes with the name of a
local
terminal or connection,
the install of the virtual terminal is rejected, and the autoinstall control
program is not invoked.
The autoinstall control program is invoked once for each virtual terminal definition to
be installed. When it is invoked, field INSTALL_SHIPPED_TERMID_PTR of the
communications area points to the supplied TERMID. Field
SELECTED_SHIPPED_TERMID contains either the supplied TERMID, or a
CICS-generated alias, depending on whether a clash of names has been detected.
Your control program can accept the TERMID passed in
SELECTED_SHIPPED_TERMID, change it, or reject the installation of the virtual
terminal.
the autoinstall control program for virtual terminals
532
CICS TS for OS/390: CICS Customization Guide