THE SENDI PROTOCOL The SENDI protocol defines a transaction calling for an expedited
one-way transfer of data. Figure 17 shows the SENDX protocol
graphically. SENDI differs from the SEND protocol in that the sink
virtual machine need not issue the RECEIVE subfunction; data is
transferred from source virtual machine storage to sink virtual machine
storage at the same time the external interrupt from CP notifies the
sink virtual machine of the transaction. Data sent by the source
virtual machine is placed in the external interrupt buffer of the sink
virtual machine. Virtual machines using the SENDX protocol are responsible for
specifying the userid for the sink virtual machine, a message ID, the
address and length of the data being sent, and the external interrupt
buffer address and data length for the sink virtual machine. A virtual machine to be used as a sink virtual machine with the SENDX protoccl
aust specify this information VMCPARM when that virtual machine
issues the AUTHORIZE subfunction. The data length specified must be at
least as long as the maximum amount of data to be transferred during a
transaction; it need not be limited to the usual 40-byte external
interrupt buffer. Effective use of the SENDI protocol requires that VMCF users agree on a maximum size for SEND X data and then issue the AUTHORIZE subfunction with the appropriate external interrupt buffer
size.
If the sink virtual machine has not provided enough SENDX buffer area
in the external interrupt buffer, CP notifies the source virtual machine that the transaction was not completed. When a SENDI data transfer is complete, CP directs a response
external interrupt to the source virtual machine, notifying it that the
transaction is complete.
r I DMKVMC I I VMCF I Interface I Module Source Virtual Machine , I I I I I I I SENDX------)----------)I I -----------------)Data I I I I <--External Interrupt--I (Final Response) t I I Figure 17. The SENDX Protocol I I I I I I I I Sink Virtual Machine I Transfer-------------------) I I --External Interrupt-----) I (Buffer Contains Data)
Part 2. Control Program (CP) 151

THE IDENTIFY PROTOCOL The IDENTIFY protocol defines a means for virtual machines to identify
themselves to other virtual machines by passing user-defined control
information via a standard VMCF message header. Figure 18 shows the IDENTIFY protocol graphically. When the IDENTIFY subfunction is issued, CP directs an external
interrupt to the sink virtual machine. Along with the external
interrupt, the sink virtual machine receives a standard VMCF message header that contains user-defined information. The IDENTIFY protocol
does not cause a response external interrupt to be directed the source
virtual machine. Source Virtual Machine DMKVMC VMCF Interface Module I I I I I I I I I I I I I I Sink Virtual Machine IDENTIFY--->---------->I I I I I I I I I--External Interrupt-------> I (IDENTIFY Sequence Complete) I I Figure 18. The IDENTIFY Protocol
152 IBM VM/370 System programmer's Guide