April 1, 1981 Segments that are to be shared in this manner must be loaded at an
address the normal end of your virtual machine and then must be
saved. The procedure for loading and saving discontiguous segments is
similar to the procedure that already exists for loading and saving
systems. Also, discontiguous saved segments can be attached to your
virtual machine in nonshared mode for testing and debugging. In
summary, a discontiquous saved segment is a segment that: • Has a name associated with it • Contains only reenterable code • Was previously loaded and saved • Can be shared by multiple virtual machines • Can be loaded bV a particular virtual machine in nonshared mode for
testing and debugging
Note: A discontiguous saved segment must not be attached by a virtual machine executing in the virtual=real area.
An example of a discontiguous saved segment is the segment of CMS that supports DOS program development and testing under eKS. This
seqment is reenterable and is named CKSOOS. The VK/370 starter system
includes an EXEC procedure that helps you load and then save this
segment. CMS contains all the necessary linkage to load the CKSOOS segment when it is needed. USER REQUIREMENTS In order to use discontiguous saved segments, you must: • Allocate permanent space on a CP-owned volume to contain the saved
segment. • Assign a name to the segment and specify where it is to be stored on
disk by defining an entry in the system name table (DKKSNTBL) with
the NAMESYS macro. • Load and save the segment. The V"/370 starter system has EXEC procedures to help you load and save the discontiguous saved segments
for CMS (one EXEC procedure to load and save CMS/DOS, one for CMS/VSAM and AMSERV, and one for the CMS Editor, EXEC processor, and OS simulation routines). • Be sure that the proper linkage for attaching and detaching saved segments is in the operating system that needs
the segment. CMS contains the linkage necessary to attach and detach
the discontiguous saved segments it supports. Usually, the direct access storage space is allocated and the system
name table entries are created during system generation. You allocate OASD space as permanent (PERM) by executing the Format/Allocate program.
This program is executed during system generation, but it is a
standalone proqram that can be executed at any time. During system
generation, you designate the CP-owned volumes by coding the SYSOWN macro the DMKSYS file. The system name table (OMKSNT) is also
created durinq system generation. If, at some time after system
generation, you wish to change the DMKSYS or OKKSNT files, you can do a
partial system generation and reassemble those files using the GENERATE EXEC GENERATE is described in the gnd You can also load and save a discontiguous saved
segment any time after system generation.
136 IBM VM/370 System Proqrammer's Guide

THE NAMESYS MACRO FOR DISCONTIGUOUS SAVED SEGMENTS Use the NAMESYS macro to define the name and location of discontiguous
saved segments. The NAMESYS macro is the same one that is used to
define the name and location of saved systems except that two of the
operands are ignored and another has a mandatory set valuee VSYSADR=IGNORE should be coded when the NAMESYS macro is describing a
discontiguous saved system. For discontiguous saved segments, the
format of the NAMESYS macro is:
label
label NAMESYS SYSSIZE=nnnnnK,SYSNAME=name,VSYSRES=cccccc, VSYSADR={IGNORE},SYSVOL=cccccc,SYSCYL=nnn, SYSSTRT=(cc,p) ,SYSPGCT=pppp, SYSPGNM=(nn,nn,nn-nn, ••• } , PROTECT = {Q! } OFF is any desired user label. SYSSIZE=nnnnnK is the minimum amount of storage you must have available in
order to load the saved system. K must be specified.
Although you must code this operand, it is not used for
discontiguous saved segments. SYSNAME=name is the name (up to eight alphameric characters) given to the
discontiguous segment to be used for identification by the SAVESYS command and FINDSYS/LOADSYS DIAGNOSE instruction.
The name selected must never be one that could be interpreted
as a hexadecimal device address (for example, "A" or "E"). VSYSRES=cccccc is the real volume serial number of the DASD volume containing
the virtual disk that is the system residence volume for the
system to be saved. This operand is ignored if VSYSADR=IGNORE. VSYSADR=IGNORE indicates that the NAMESYS macro is describing a system or
segment that does not require a virtual system residence vo:ume. Code VSYSAta=IGNORE .heL you are discontiguous saved segment. SYSVOL=cccccc is the volume serial number (up to six alphameric characters)
of the DASD volume designated to receive the saved system.
This must be a CP-owned volume. Part 2. Centrol Program (CP) 137