Loading and Saving Discontiguous Saved Segments Loading and Saving Discontiguous Saved
Segments
After you have finished generating and testing your new system, you may
wish to load and save discontiguous saved segments. The DMKSNT module
supplied with the starter system includes entries for saved segments
called CMS, CMSSEG, CMSVSAM, CMSAMS, CMSDOS, and INSTVSAM. You may also create_ your own entries. See the section "Preparing the System Name
Table File in Part 2.
Throughout the following discussion, it will be helpful for you to
refer to Figure 31, which shows how the CMS discontiguous saved segments
are loaded in virtual storage if you use the DMKSNT module supplied with
the starter system.
Before a discontiguous saved segment can be attached and detached by
name, it must be loaded and saved. The discontiguous saved segment must
be loaded at an address that is beyond the highest address of any
virtual machine that will attach it. It is the system programmer's
responsibility to make sure the saved segment is loaded at an address
that does not overlay the defined virtual machine or any other saved
segment that may be attached at t-he same time. The load addresses are
determined by the entries you coded in your DMKSNT module.
The load address for the discontiguous saved segment should be just
beyond the largest virtual machine that uses it. If the load address is
unnecessarily high, real storage is wasted because CP must have segment
table entries for storage that is never used.
For example, assume you have five CMS virtual machines in your
installation. Also assume that all five use the CMS support for DOS program development and testing which is in a 32K segment named CMSDOS. If each of your five CMS virtual machines has a machine size of 320K, you should load the CMSDOS segment just beyond 320K but below 992K (so
as to contain it within 1M). Otherwise real storage would be wasted
because CP must maintain segment table entries for each 1024K of
storage. Once the named segment is loaded at the correct address, you can save
it by issuing the CP SAVESYS command. To be sure that a discontiguous
saved segment has storage protection, set the storage key for the
segment accordingly. CMS has a new command, SETKEY, to do this. The CMS SET KEY command is described in the 1M/310 Guide. CMS has EXEC procedures that help you load, set storage keys for, and
save the CMS discontiguous saved segments. The DOSGEN EXEC procedure
loads and saves DOS segments. The VSAMGEN EXEC procedure loads and
saves the CMS/VSAM and Access Method Services segments. The CMSXGEN EXEC procedure loads and saves CMSSEG, which contains the CMS Editor, EXEC processor, and OS simulation routines. You used the CMSXGEN EXEC procedure to save CMSSEG in Step 24 of the system generation procedure.
The DOSGEN and VMSAMGEN EXEC procedures are described later in this
section.
Note: These procedures for loading and saving discontiguous saved
segments and the associated text files are 'mode l' to reduce the amount
of storage needed for the master file directory in the user's virtual
machine. The system disk must be accessed (any mode, A through G)
before loading any discontiguous saved segment. Make sure that this is
done any intermediate IPL of CMS. Part 3. Generating VM/310 (CP, CMS, RSCS, and IPCS) 261

Loading and Saving Discontiguous Saved Segments
Decimal
Load Segment 16320K 16256K
2112K 2048K I Contains the CMS/DOS discontiguous saved 1 , segment used to install VSAM and Access I , Method Services. , ,INSTVSAM FEOOOO(1) 4064(2) 254(3), Storage unaddressable by the virtual I , machine. , , 210000 528 33 I -------------END OF DEFINED VIRTUAL STORAGE------------I Contains the CMS control blocks and free
storage used during installation of the
segments. 200000 512 32 I , , , , -------------------------------------------------·-----------1 CMSDOS Contains DOS/VS Simulation Routines
The area from 1984K to 2016K is shared.
The area from 2016K to 2048K is unused. 1FOOOO 496 31 1984K I , Contains CMS Access Method Services support
The area from 1472K to 1856K is shared; I I , CMS AMS the area from 1856K to 1984K is not. 170000 368 23 1472K ,--------------------------------------------------------- , , , I CMSVSAM 1088K 1 , I I , CMSSEG Contains CMS VSAM support
The area from 1088K to 1408K is shared;
the area from 1408K to 1472K is not. 110000 272 17
contains the Editor, EXEC, and OS Simulation
Routines
The entire segment is shared. 100000 256 16 1024K 1----------------------------------------------------------- , I I CMS Virtual Machine's Area 000000 0 OK 1---------------- , I (1) HEX LOAD ADDRESS
(2) STARTING
PAGE NUMBER o
(3) STARTING SEGMENT NUMBER .J
Figure 31. Sample Layout of Storage for CMS Discontiguous Saved Segments You may want to compare this storage layout with the sample DMKSNT shown in the section "Preparing the Name Table File (DMKSNT)" in
Part 2. Note that as new releases of VSAM and AMS become available, the
number of segments required by these systems may be increased, thus
requiring all segment addresses above these segments to be increased
accordingly. Noie: Refer to the latest Memo to Users for any possible changes to the
sample layout of storage for CMS discontiguous saved segments.
268 IBM VM/370 Planning and System Generation Guide