must contain the userid of the sink virtual machine. The status of
the specified sink virtual machine is not checked by the control
program (CP) at this time. VMCPPRTY (X'40')
Indicates, for SEND, SEND/RECV, SENDX, and IDENTIFY
requests, a PRIORITY message request. For an AUTHORIZE request, it indicates an AUTHORIZE PRIORITY request. You
cannot send PRIORITY messages to another virtual machine
unless that virtual machine has been authorized for PRIORITY messages. The SEND and RESPONSE external interrupts for a PRIORITY message are queued ahead of pending non priority
external interrupts. VMCPSMSG (X'20')
Indicates that the virtual machine accepts messages sent via the
SMSG command.
Bits 3 through 7 are reserved for IBM use.
V*2
(VMCPFLG2)
Reserved for IBM use. VMCPFUNC Contains the halfword DIAGNOSE X'68' subfunction code that
defines the VMCF subfunction being requested as follows:
Hexadecimal
Command Code Subfunction VMCPAUTH X'OOOO' AUTHORIZE VMCPUAUT X'OOOl' UNAUTHORIZE VMCPSEND X'OOO2' SEND VMCPSENR X'OOO3' SEND/RECV VMCPSENX X'OOO4' SENDX VMCPRECV X'OOOS' RECEIVE VMCPCANC X'OOO6' CANCEL VMCPREPL X'OOO7' REPLY VMCPQUIE X'OOO8' QUIESCE
VMCPRESM X'OOO9' RESUME VMCPIDEN X'OOOA' IDENTIFY VMCPRJCT X'OOOB' REJECT VMCPMID Contains a unique message identifier associated with a transaction.
The source virtual machine must originate the message ID for SEND,
SEND /RECV, and SENDX requests. The message ID is used by the
sink virtual machine (along with VMCPUSER) to respond to the
source request with a RECEIVE, REPLY, or REJECT request. The
message ID allows the sink virtual machine to selectively RECEIVE, REPLY, or REJECT messages when more than one message is
enqueued. The message ID is used by both the source and sink as a
unique identification for all messages. You may send messages with
the same message ID to multiple users; you cannot send multiple mes­
sages with the same message ID to one user. Once a transaction is
completed, however, the message ID may be reused.
The Virtual Machine Communication Facility 99

VMCPUSER Specifies the userid of the sink virtual machine for SEND, SEND/RECV, SENDX, IDENTIFY, and CANCEL requests and the
userid of the source virtual machine for RECEIVE, REPLY, and
REJECT requests. The sink virtual machine uses this field in combi­
nation with the message ID (VMCPMID) to respond to source
requests. When the original source parameter list VMCP ARM is
passed to the sink as themessage header VMCMHDR, the userid is
changed from sink to source.
This field is also used to specify the SPECIFIC userid for an
AUTHORIZE SPECIFIC request. VMCPVADA Contains one of four addresses, depending upon which VMCF sub­
function is requested:
For SEND, SEND/RECV, and SENDX requests, VMCPVADA con­
tains the address of the source virtual machine data. For RECEIVE
requests, VMCPV ADA contains the address of a sink virtual machine
RECEIVE buffer. For REPLY requests, VMCPV ADA contains the
address in sink virtual machine storage where REPLY data is located.
For an AUTHORIZE request, VMCPV ADA specifies the address of
the virtual machine external interrupt buffer.
The length of the associated data or buffer is specified in the VMCPLENA field. VMCPLENA Contains the length of the data sent by a user, the length of a
RECEIVE buffer, or the length of an external interrupt buffer, which­
ever is specified in the field VMCPV ADA. The size of the value spec­
ified in VMCPLENA is restricted only by virtual machine storage size.
The sink virtual machine can use the value in this field as the data
length for RECEIVE operations. VMCPVADB Contains the address of a source virtual machine's REPLY buffer for
a SEND /RECV request. When the sink virtual machine issues a REPLY in response to a SEND /RECV from the source virtual
machine, the REPLY data is moved in this buffer. The length of the REPLY buffer is contained in the field VMCPLENB. VMCPLENB Specifies the length of the source virtual machine's REPLY buffer.
The sink virtual machine uses this field to determine the maximum
length of the REPLY. A corresponding field within the response mes­
sage header contains a residual data count. The source virtual
machine uses this residual count to determine the length of the sink
reply. The original REPLY buffer length (less the residual count) is
the length of the REPLY from the sink virtual machine. VMCPUSE Contains the VMCF user doubleword. The user double word is trans­
mitted to the sink virtual machine in the SEND message header for SEND, SEND/RECV, SENDX, and IDENTIFY requests. For 100 VM/SP System Programmer's Guide