TRAMSGLM lUCY message limit to be specified for CONNECT
TRAUDAT A IPUSER from lUCY external interrupt buffer
For inbound: QUIESCE, RESUME, CONNECT for LU For outbound: ACCEPT
YM userid
For inbound: CONNECT for YTAM service machine
For outbound: SEYER LUNAME
For inbound: SEYER TRAUDITl lUCY IPAUDITl flags from IXBLOK (used for
TRAYSARP,TRAYSAMC)
TRAUDIT2 lUCY IPAUDIT2 flags from IXBLOK (used for
TRAYSARP,TRAYSAMC)
TRAINSTR Addr of last instruction issued before invoking abend routine
(TRACTLBK)
TRA YMADR Current YlvfBLOK address-used for abend situations
(TRACTLBK) SNA Virtual Console Communication Services 191

The Message System Service
The Message System Service is a CP system service. It allows a virtual machine to
read incoming messages and responses from CP, as opposed to displaying them on
the terminal.
Establishing Communications "*MSG" is the assigned Message System Service userid. Communications are
established with the Message System Service (*MSG) via IUCV. The IUCV DECLARE BUFFER function is invoked by the virtual machine to allow commu­
nications with IUCV, and the IUCV CONNECT function is invoked to establish
the communications path to the *MSG system service.
The types of messages that the virtual machine can receive are controlled by speci­
fying the IUCV parameter on the CP SET command. For example, if a user has
specified "CP SET MSG IUCV", all messages received via the CP MESSAGE
command are sent to the virtual machine via IUCV. IUCV signals the receiving
virtual machine with an external interrupt. The message may be retrieved by using
the IUCV RECEIVE function and may be used by a program running in the virtual
machine.
Note: For a complete list of the CP SET commands that can use the IUCV param­
eter, see VM/SP CP Command Reference for General Users.)
The Message System Service identifies the source of the message it intercepts by a
code in the IUCV message class field. The message source is interpreted as
follows:
Class Message Source
1 Message sent using CP MESSAGE (MSG) or CP MSGNOH 2 Message sent using CP WARNING (WNG)
3 Asynchronous CP messages and CP responses to a CP command exe­
cuted by a virtual machine using *MSG
4 Message sent using CP SMSG command
5 Any data directed to the virtual console by the virtual machine
(WRTERM, LINEDIT, etc.)
6 Error message from CP (EMSG)
7 Information messages for CP (IMSG)
8 Single Console Image Facility (SCIF) message from CPo
Error and information messages (classes 6 and 7) are types of CP messages and are
included in class 3 when EMSG and IMSG are not specifically set to IUCV via the
CP SET commands.
The format of the data received from IUCV is as follows:
192 VM/SP System Programmer's Guide