Alternating Between eMS and DOS/VS Under VM/370 When working in a development and testing environment (rather than in a Latch envirenment) and the work is not suitable for these are seme advantages to alternating between CMS and DOS/VS: • Reduced unit record output. Under CMS, users can examine program output and compiler listings online, check the results and resubmit
the job without printing a single page on the system printer or
punching card decks. • Faster turnaround time compared with batch alone; under CftS, users
can see the results of program compilation and execution immediately,
rather than waiting for output from a batch system.
This topic outlines the technique for alternating between operating
systems. Before using this technique, users should be familiar with CMS, the conversational component of Vft/370, particularly with the ces editor and seme file system commands. CftS usage information is in For details on CftS commands and EDIT
subcommands, refer to LOADING CMS INTO A VIRTUAL MACHINE Te lead CftS into a virtual machine, use the IPL command. Usually, IFL CMS by specifying the sa ved system name CMS: ipl cms Or, load CMS by specifying the virtual address of the CftS system, which
is usually 190: ipl 190 After receiving a message like this: CMS VERSION 3.0 A user can use the interactive facilities of ces to prepare jobs for
execution in the DOS/VS virtual machine. USING THE CMS EDITOR TO PREPARE JOBS Use the EDIT command in CMS to pass control to the eMS editor for
preparing disk files of SO-character card image records. The created
files may contain DOS/VS job control statements, source files, or even IPL decks.
For example: To IPL DOS/VS using input statements from the card
reader, prepare CMS files that contain: • The DOS/VS supervisor name required for an IPt, such as the record: $$A$SUP1 94 IBM VM/370 Operating Systems in a virtual Machine

• The IPL control statements that a user wants to supply, such as:
set
dpd
assgn sysrec,x'250'
set rf=yes
log
Assume for the purposes of this example that: (1) these files have file identificaticns of SUPER JCL and START JCL, and (2) in these files
are all the statements needed to control DOS/VS IPL. The CMS editor can also be used to prepare the job stream selected
for execution. For example: To assemble an assembler language source and make the source file available as a disk file, edit the
file and insert the DOS/VS job control statements into the file.
The file DOSTEST JCL might contain: II JOB TESTl II OPTION NODECK II EXEC (assembler language source statements) 1* 1& Although this job stream contains only
necessary to assemble the job, it can
necessary tc link-edit the output module, on: the job control statements
also include the statements
catalog the program, and so ISSUING SPOOL COMMANDS TO CONTROL UNIT RECORD DEVICES Before sending a job to the DOSIVS virtual machine, check the unit
record devices: • Close and purge the card reader, to make sure no files are left over
from a previous job:
spocl reader nocont
close reader
purge reader all • Close and purge the card punch, and spool it to the card reader: punch nocont
close punch purge
spocl punch to * When using the card reader to 1PL DOS/VS, spool the punch least the first two files must be separate spool files. Section 3. DOSIVS in a Virtual Machine 95