ALTERNATING BETWEEN OPERATING A virtual machine user may require the facilities of more than one system during a single terminal session. When running an system from a terminal, use the CMS editor
to create and modify job streams and to analyze the results and output. programmers who normally use CftS to interactively create,
medify, and test programs, may require facilities for compilation or
execution that are not supported or available in The technique described in this topic uses multiple operating systems
consecutively. Job control cards, compiler or assembler source
programs, and test data streams are created and modified at the terminal
under control of the editor. The job stream is then executed, by
passing control to an appropriate operating system that has the
necessary facilities.
In this way, the programmer uses the terminal-oriented facilities of CMS to create and update source programs and JCL. When ready to compile or test, he can give control of his virtual machine to the operating
system. After execution is finished, he can give control back to CMS to
selectively scan and display printer and punch output at the terminal.
This approach assumes that the programmer has created source program files and data files under CMS. To execute under another operating system (in this example, OS), the programmer must also create JCL
records that specify the compilation, link editing, or execution, as
appropriate. These records are created under CftS and named with a
distinctive filename and filetype (for example, PLICOMP JCL). Job
control records, source program files, and data files can then be merged
together in the virtual card reader to form a single OS job stream. The
CP and commands (shown in Figure 3) create and transfer this job
stream.
The CP SPOOL com.and transfers subsequent (not currently existing) card images from the virtual card punch of one virtual machine to the virtual
card reader of that same or SOme other virtual machine. During this
time, no real cards are punched or read; V8/310 manages the transfer of card-image data files through disk spooling operations only.
Figure 3 shows how to punch files to the virtual machine's card
reader. The virtual machine is in the CMS environment at the start of
the example. The com.and "SPOOL OOc cont eof" specifies that reading be
continuous until all files spooled to the virtual machine are exhausted
and the virtual end-of-file button on the reader is pushed. NOBEAD!E specifies that no special control cards are to be inserted at the
teginning of each punched file. Virtual device 230 is an OS system voluae. Virtual device 231 contains the OS job queue, SYS1.SYSJOEQ!. All standard eMS and OS responses are omitted from the example; however,
the OS READY message is included to more fully illustrate the 1Ft sequence. Also, assuming that the user has a 2141, he must press the
attention key before entering each OS command. The attention
interruptions are not shown in Figure 3.
24 IBM VM/370 Operating Systems in a Virtual Machine

r-------------------------------------------------------------------------, CMS cp close OOc cp purge OOc all
cp close OOd purge
cp spool OOd to * cont
punch jobcard jcl (noheader)
punch pliccmp jcl (noheader)
punch plimain pli (noheader)
punch asmcomp jcl (noheader)
punch asmsub assemble (noheader)
punch linkgc jcl (noheader)
punch godata dat (noheader)
punch slshstar jcl (noheader)
cp spool OOd nocont
cp close OOd cp spool OOc cont eof
cp ipl 230 N0ig: The following are issued once under OS control: IEE007A READY set date=xx.355,Q=(231)
start rdr,OOc start wtr,OOe start
Figure 3. OS Job Stream Transfer
To transfer files between systems, the user must have access to both operating systems being used. Access to both systems can be provided either in the virtual machine's VM/370 directory entry, or dynamically
before loading the new system.
Figure 4 illustrates a virtual machine configuration and the
corresponding VM/370 directory control statements. Virtual device
addresses 190 and 191 contain the CMS system and user disk area. Virtual device addresses 230 and 231 contain the OS system and user disk
area. The two systems use a common card reader, card punch, printer,
and console.
r-------------------------------------------------------------------------, USER OS2 PASSWORD ACCOUNT NUMBER BIN16 CONSOLE 01F 3215 SPOOL C 2540 READER SPOOL D 2540 PUNCH SPOOL E 1403 LINK JFK 230 230 R
LINK CMSSYS 190 190 RR MDISK 231 2314 120 82 UDISK1 WR MDISK 191 2314 101 10 DDISK1 WR RPASS WPASS Figure 4. Directory Entry for Alternating Between Operating Systems I I I I I I I I , I Section 1. General Considerations 25