DMSINS ---Clears DCSSAiAL and ensures that all the parameters on the co •• and
line are valid; branches back to label INITLOOP to reprocess for the
segment just saved. If BATCH is specified, sets BATFLAGS and BATFLAG2 in NUCON. Saves the name of the saved system in SYSNAME in NUCON. Issues ACCESS 195 A to access the batch virtual machine A-disk. DMSI!2 Issues DIAGNOSE 60 to get the size of the virtual machine; sets up
enough storage for this virtual DMSINS ---rl-the DCSSAiAL flag is set, sees if the size of the CMSSEG segment
overlaps the size of the virtual machine. If this is the case, DMSINS sets the flag DCSSOiLP and continues the initialization
procedure for a CMS virtual machine running without the use of the CMSSEG segment, that is, performs time-of-day processing and OS initialization.
If the CMSSEG segment can be used, DMSINS issues the DIAGNOSE 64 LOADSYS function as the final check to see if the segment is usable.
If the segaent is loaded successfully, it can be used whenever one of
the functions contained in it is requested. Because it is not
required immediately, DMSINS issues the DIAGNOSE 64 PURGESYS function
to purge the segment. If the segment cannot be successfully loaded, DMSINS turns off the DCSSAiAL flag. INITIALIZE OS SiC-HANDLING WITHOUT THE USE OF THE CMSSEG SEGMENT DMSINS ---Checks for the availability of CMSSEG. DMSSTT ---FInds and returns the address of DMSSiT, the CMS as SVC-handler. Acquires enough free storage to contain DMSSVT. DMSLOA ---roads DMSSVT. Sets the flag DCSSVTLD. DMSINS ---rf-the BATCH virtual machine is not being loaded, determines whether
there is a PROFILE EXEC or a first command line to be handled. If
so, issues SiC 202's to process these commands and passes control to DMSINT, the CMS console manager. If the BATCH virtual machine is being
accesses the D-disk and passes control
manager.
initial program
to DMSINT, the
loaded,
console CMS Method of Operation and Program Organization 2-59

Initializing a Named or Saved Systems
A named system is a copy of the nucleus that has been saved and naaed with the CP SAVESYS co •• and. It is faster to IPL a na.ed syste. than to
IPL by disk address because CP maintains the named system in page for.at
instead of CMS disk for.at. That is, the saved system is on disk in 4096-byte blocks instead of 800-byte blocks. The initialization of a
saved system is also faster because the SSTAT is already built.
The shared system is a variant of the saved system. In the shared
system, reentrant portions of the nucleus are placed in storage pages
that are available to all users of the shared system. Each user has his own copy of nonreentrant portions of the nucleus. The shared pages are
protected by CP, and may not be altered by any virtual machine.
During DMSINI processing, the virtual machine operator
the nucleus must be written (via message DMSINI607R) • If
answers no, control passes directly to DMSINS to initialize
saved system specified by the operator in his answer DMSINI606R. is asked if
the operator
the nailed or
to aessage Handling the First Command Line Passed to CMS DMSINT, the CMS console manager, contains the code to handle commands stacked by module DMSINS during initialization processing. DMSINT checks for the presence of a stacked command line, and if there is one
to process, processes it just as it would a ccmmand entered during a
terminal session. That is, DMSINT calls the iAITREAD subroutine and
issues an SVC 202 to execute the command. When first command processing
completes, DMSINT receives control to handle co •• ands entered at the
console for the duration of the session.
Setting and Querying Virtual Machine Environment Options DMSSET sets up
the publication
these settings
structured and DMSSET. the virtual .achine environment options, as outlined in ££!!sng DMSQRY displays
at the user console. Both of these modules are
relatively easy to follow, except for so.e sections of DMSSET: SET DOS ON (VSAM) PROCESSING DMSSET ----(label DOS) If a disk mode is specified on the command line, ensure
that it is valid. DMSLAD ---rf-the disk mode specified is valid, locates and returns the address
of the disk. Issues DIAGNOSE 64 FINDSYS to locate the CMSDOS segment. If the
segment is not already loaded, issues DIAGNOSE 64 LOADSYS to load it. 2-60 IBM VM/370 System Logic and Program Determination--Voluae 2