OS/MVS Simulation History
When the VM operating system was being developed, applications and licensed programming products were already running under the OS/VS1 or DOS operating systems. The VM designers saw the need to allow these applications and program products to run in the new VM environment where our customers could use them for new program development and testing, a major task for almost every customer shop. Because the available IBM licensed products had to run in both operating environments, we needed to develop a subsystem which would allow them to use the OS interface on VM. The CMS OS Simulation subsystem was developed to satisfy that requirement.
Today, many basic OS/MVS functions are supported using the CMS OS Simulation subsystem. You should note that it does not support all of either the OS/MVS macros or the SVC functions. The subsystem was intended to support just those functions needed to allow the IBM program products and featured applications to run under VM/CMS with little or no modification of the program products themselves. A list of the OS/MVS macros and SVC functions that CMS supports can be found in Table 1, Table 1, Table 1, and Table 1.