DIAGNOSE Instruction I X'83' I Rx I Ry I Rx VMBLOK = VMPXINT VMCPNT XINTBLOK Queue
1 X'4001' I X'0068' VMCPARM . VMCBL.,OK Queue -.,11 I. Master VMCBLOK - VMCVADA External Interrupt Buffer ---. (VMCMHDR) --------- Optional SENDX Data Buffer
Figure 13. VMCF Control Block Relationships
should specify the size as 169 bytes (roo. for a 40-byte header and a 120- to 129-byte aessage buffer, depending on the length of the co •• and
and userid).
Setting SMSG ON can be accoaplished by setting the S8SG flag on in
the VMCF paraaeter list when issuing an AUTHORIZE. It aay also issue
the CP co •• and SET S!SG ON. Either aethod sets the Special Bessage flag
on in the VMBLOK. When this is done, any other virtual aachine can
issue the SMSG co •• and to the userid of the receiving virtual aachine. CP Introduction 1-41

If the receiving virtual machine chooses not to accept special messages at any time, it can merely issue SET S8SG OFF. CP would then inform any machine issuing the SMSG command that the virtual machine is
not receiving special messages. When it is ready to resume accepting
special messages, the machine need only to issue SET S8SG ON. The following shows the processing when an SMSG command is issued.
r 1 S8SG userid msgtxt
, 1 CP: 1 • Validates S8SG command. 1 • Checks that receiving virtual machine 1 has Special Message flag ON (in receiving 1 If not --1----------, • Checks for receiving virtual machine being 1 1 authorized with CP. If not--- --------->1 • Obtains storage for containing one VMCF I ,---------- External Interrupt Buffer. ISend message to • Builds VMCF parmeter list: lissuer that I - saves buffer address in VKVMVADA Ireceiving machine I - computes message length & stores that lis not receiving I length in VKVMLENA Ispecia1 messages I - mOves message test into area pointed to ' I ' BY VMCMBUF (VMCMVADA value minus 40 1 bytes) for the computed length of the , message text EIIT
- stores SENDI subfunction code in VMCMFUNC - stores CPU clock value in VMCMMID as a
unique message-id • Calls DMKVMC to execute SEND I subfunction
code to send the message to the receiving
virtual machine. I , , Receiving virtual machine processes datal
fro. buffer transmitted via SENDI. I During a Special Message session, the following error messages could be
sent back to the issuer of the SMSG command: DMKMSG003E: DMKKSG020E: DKKKSG04SW: DMKMSGOS7E: INVALID OPTION - option USERID MISSING OR INVALID userid NOT LOGGED ON userid NOT RECEIVINGi [DISCONNECTED I MSG OFF I SMSG OFF I NOT AUTHORIZED I WNG OFF] 1-42 IBM V8/370 System Logic and Problem Determination--Vo1ume 1