Pg. of GC20-1819-2 Rev March 30, 1979 by Supp. SD23-9024-1 for 5748-XX8 I I I I I I I ncss I I I I I I I Loader Tables User Program Area CMS Nucleus
Transient Program Area
Free storage used by CMS routines
Low-storage CMS routines
System Control Blocks,
Pointers, Flags
Figure 19. Simplified eMS Storage Map , X'n' (where n = your
virtual machine
storage size) X'20000' X'10000' X'ECCO' X'80CO' X'40CO' the area shown
is known to CP the CMS system
using eMS, you
command to load
same system, CP as the CMS nucleus is loaded with the CMS system, which
by its saved name, eMS. This saved system is a copy of
that is available for many users to share. When you are
share it with other users who have also issued the IPL the saved CMS system. By having many users share the
can manage system resources more efficiently. Under some circumstances, you may need to lead the CMS system into
your virtual machine by entering the IPL command as follows:
cp ipl 190 This IPL command loads the eMS system by referring to its virtual
address, which in most installations is 190. The copy of CMS you load
this way is ncnshared; it is your own copy, but it is the same system,
functionally, as the saved system CMS. Some of the CP and eMS debugging commands do not allow you to trace
or store information that is contained in shared areas of your virtual
machine. For example, if you have entered the command:
cp trace inst
224 IBM VMj370 CMS User's Guide

to trace instructions in your virtual machine, some of the instructions
may be located in the CMS nucleus. If you have shared copy of CMS, you
receive a message like: DMKATS181E SHARED SYSTEM CMS REPLACED NON SHARED COpy
and CP loads a copy of eMS for you that you do not share with other
users. Some CMS routines and programs are stored on disks and loaded into
storage as needed. These segments include the CMS editor, EXEC processor, and as simulation routines; eMS/DOS; VSAM; and access method
services. Beyond the end of your virtual machine address space is an
area of storage into which these segments are loaded when you need them. Since this area is not contiguous with your virtual storage, the
segments that are loaded in this area are called discontiguous saved
segments.
These segments are loaded only when you need them, and are released
fro. the end of your virtual machine when you are through using them.
Like the CMS system, they are saved systems and can be shared by many
users. For example, whenever you issue the EEIT command the segment
named CMSSEG is loaded; when you enter the ErIT subcommands FILE or QUIT, the saved system CMSSRG is released= The other segments are named CMSDOS (for CMS/DOS), CMSVSAM (for VSAM interfaces), and CMSAMS (fer
access method services interfaces). These names are the defaults; they
can be changed by the installation. You can specifically request a nonshared copy of a segment ty loading
the named system by volume rather than by name. If you do not do this
before altering a shared segment (unless with the AtSTOP, TRACE, or STORE CP commands), CP issues the message DMKVMA456W and places you in
console function mode.
In additien, for the CMSSEG segment only, you can indicate an
alternate segment to be loaded on the IPL command. The format of the
IPL command to support this is:
IPL { cuu PARM SEG=segmentname systemname J
SEG=segmentname
indicates the name of the saved segment to be loaded whenever the CMS editor, EXEC Frocessor, or OS simulation routines are needed.
Eight characters must be entered for segmentname; either assign an
eight-character segment name when you code the NAMESYS macro fer
your installation, or be sure that the operato£ enters trailing
blanks if segmentname is less than eight characters long.
The CMS batch facility loads whatever segment is specified
first IPL command issued for the batch virtual machine. Thus,
first IPL command for a CMS batch facility machine is:
IPL CMS PARM SEG=CMSSEG02 on the
if the
all subsequent IPL commands issued by the eMS batch facility will
sFecify the same segment name (CMSSEG02). For additional information on
segments, and CMS virtual storage, saved systems, discontiguous saved
see the Section 11. How VM/370 Can Help You £ebug Your programs 225