Introduction The DMKMSS program operates under the
control of either OS/VS1 or OS/VS2 eMVS) in
a virtual machine. It is a communications
interface between the VM/370 control
program and the MSS Mass Storage Control. It a co.nination of CP-generated attention interrupts on a virtual I/O device, the DIAGNOSE code X'78' instruction, and OS/VS SVC 126 to provide
coaaunications.
Chapter 12. DMKMSS-The MSS
Communicator
Requests are received from VK/370 in
response to a DIAGNCSE code X'78' instruction issued by DKKKSS. They are
passed to the MSC using the standard as/vs SVC 126. Responses are received frem the MSC and returned to VM/370 using DIAGNOSE. Chapter 12. D!KKSS--The MSS Communicator 223

Method of Operation
This section describes the two major
sections of the D!K!SS prograa. Diagra. 12-1 shows initialization using OSjVS control blocks.
DMKMSS I r
Diagram 12-1
DMKMSS Initialization Diagraa 12-2 shows the processing of a V!/310 request.
Figure 12-1 shows the relationship of
these diagraas. I Diagram 12-2
DMKMSS
Processing
Figure 12-1. Key to the D!KMSS Method of Operation Diagrams
224 IBM VM/310 Service Routines Program Logic