The IBM Virtual Machine Communication Facility (VMCF) is a feature of the VM/370 operating system introduced in Release 3 in 1976. It "provides a method of communication and data transfer between virtual machines operating under the same VM/370 system."
VMCF uses paravirtualization through the diagnose instruction VMCF <code>SEND</code> function to send data, in blocks of up to 2048 bytes, from one virtual machine to another. The receiving virtual machine accesses the data thru the diagnose <code>RECEIVE</code> function. It provides a simpler interface and greater performance than the prior use of virtual channel-to-channel adapters for the same purpose.
VMCF was superseded by the Inter User Communication Vehicle (IUCV), introduced in 1980 with VM/SP.