Important
Information in this chapter about the CCIN and CTIN transactions, the
EPI, Client virtual terminals, and the Client terminal emulator function,
applies to:
- CICS® Transaction Server for z/OS®
- CICS Transaction Server for OS/390®
- CICS Transaction Server for VSE/ESA
There are some restrictions on CICS on System/390® support for CICS Clients.
The following general restrictions apply:
- The CCIN and CTIN transactions (invoked by the Client to exchange connection
details with the server and to install Client terminals) can run only on a CICS system that is directly connected to the Client. A CICS system that
is directly connected to the Client can, however, use normal transaction routing
and function shipping flows to communicate with any other CICS system.
If an EPI request is routed to a back-end AOR, the AOR can be any currently-supported
release of CICS.
If an ECI request is to a back-end AOR, the AOR must be
one of the following:
- CICS Transaction Server for z/OS
- CICS Transaction Server for OS/390
- CICS Transaction Server for VSE/ESA
- CICS/VSE 2.3
- CICS/400
The information passed by the Client to CICS on System/390 by means of
the CCIN transaction is not passed by CICS on System/390 to a back-end AOR.)
- APPC connections to Clients support data synchronization levels (synclevels)
0 and 1 only.
- When acting as a server to a CICS Client using the EPI, CICS on System/390:
- Does not support the use of a PF key specified on the TASKREQ option of
a TRANSACTION definition to start the transaction from a Client virtual terminal.
- Does not support use of the print key specified on the PRINT system initialization
parameter from a Client virtual terminal.
- Does not display the good morning panel when a Client terminal is installed.
Note that you can use the CICSTERM command to specify the initial transaction
for a CICS Client.
- You can make only limited use of VTAM® persistent sessions support to recover
APPC
connections to Clients automatically after a failure. If
you define your Client connections to use persistent sessions, the only sessions
that are recovered are those on:
- Statically defined
APPC
connections
- Autoinstalled single-session
APPC
connections.
These sessions are recovered only if:
- No virtual terminals were installed on the connection at the time of the
failure.
- For autoinstalled connections, the value of the AIRDELAY system initialization
parameter is greater than zero.
- You can use the execution diagnostic facility (EDF) in single-terminal mode from a Client emulator, to test
a CICS on System/390 server transaction.
EDF in two-terminal mode is supported only
when both of the terminals and the transaction reside on the same CICS system; that
is, when no Client terminal is involved.
- When running a Client emulator, you cannot use the CESN or CESF transactions
to sign on to (or off from) the CICS region to which the Client is directly
attached.
- EPI server transactions running in
the CICS region to which the Client is directly attached can issue EXEC CICS SIGNON or SIGNOFF commands only if the virtual terminal has been installed
as signon capable.
Note:
Transactions started at a virtual terminal
installed as signon capable are executed with the authorities assigned to
either the default user defined by the DFLTUSER system initialization parameter
or the user currently signed on at the terminal.
- You cannot install more that 512 virtual terminals per Client connection.
This limit is necessary to prevent service attacks. An attempt to install
more than 512 virtual terminals results in message DFHZC3206; the request
to install the virtual terminal is rejected. A response code of DISASTER with
a reason code of INVALIDREQUEST is sent to the Client.
- You cannot use preset security with Client virtual terminals.
- You cannot use the EXEC CICS or CECI ISSUE PASS command with Client
virtual terminals. (ISSUE PASS is used to disconnect a VTAM terminal from CICS, and transfer it to another CICS terminal-owning region.)
- On CICS System/390 products other than CICS Transaction Server for OS/390 Release 3, the CEMT INQUIRE TERMINAL command
does not return information about Client virtual terminals. However, the EXEC CICS INQUIRE TERMINAL command does.
- If you discard or reinstall a (statically defined or autoinstalled) connection
to a Client workstation, and the connection is in use, the workstation end user must shut down and restart the Client before
being able to continue.
For APPC connections to Clients
, if you discard or reinstall
a (statically defined or autoinstalled) Client virtual terminal, and the CTIN
transaction has been run to install or reserve the terminal but not to release
it, the workstation end user must restart the EPI program or terminal emulator
that uses the virtual terminal, if he or she wants to continue to use it.
As well as these general restrictions, there are some restrictions on server
programs invoked from the ECI and EPI--see Application programming for Clients.
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