When an I/O operation completes, CMS/DOS posts the CCB with the return code. Partial RPS (rotational position sensing) support is
available for I/O operations to CMS disks because CMS uses RPS in its
channel programs. However, RPS is not supported when real DOS disks are
read. DOS/VS Supervisor Control Blocks Simulated by CMS/DOS CMS/DOS supports DOS/VS program development and execution for a single
partition: the background partition. Because eMS/DOS does not support
the four foreground partitions, it also does not simulate the associated
control blocks and fields for foreground partitions. CMS/DOS does
simulate the following DOS/VS supervisor control blocks: • ABTAB--Abnormal Termination Option Table • BBOX--Boundary Box • BGCOM--Background Partition Communication Region • EXCPW--Work area for module DMSXCP • FICL--First in Class • LUB--Logical Unit Block • NICL--Next in Class • PCTAB--program Check Option Table • PIBTAB--Program Information Table
• PIB2TAB--Program Information Block Table Extension • PUB--Physical Unit Block • PUBOWNER--Physical Unit Block Ownership Table
• SYSCOM--System Communication Region
For detailed descriptions of CMS/DOS control blocks, refer to the £2n!E21 §lg£! #QS!£. User Considerations and Responsibilities
A critical design assumption of CMS/DOS is that installations that use CMS/DOS will also use and have available a DOS/VS system. Therefore, if
you want to use CMS/DOS you must first order and install a DOS/'S system, Release 31, 32, or 33. Also, if you want to use the DOS/iS COBOL and DOS PL/I Optimizing compilers under CMS/DOS, you must order them and install them on your DOS/iS system.
There are several other facts you should consider if you plan CMS/DOS. The following sections describe some of the
considerations and responsibilities. DOS/VS System Generation and Updating
Considerations
to use
user
The CMS/DOS support in
provides the necessary
and system routines
Optimizing compilers image libraries. CMS may use a real DOS/VS system pack. CMS/DCS path and then fetches DOS/VS logical transients
directly from the DOS/VS COBOL and DOS PL/I directly from the DOS/VS system or private core
It is your responsibility to order a Release 31, 32, or 33 DOS/VS system and then generate it. Also, if you plan to use DOS compilers,
you must order the current level of the DOS/VS COBOL compiler and DCS PL/I Optimizing compiler and install them on the same DOS/VS system. 306 IBM VM/370 System Programmer's Guide

When you install the compilers on the DOS/VS system, you must
link-edit all the compiler modules as relocatable phases using the following linkage editor control ACTION REL You can place the link-edited phases in
core image library. either the system or the When you later invoke the compilers from CMS/DOS, the library (system
or private) containing the compiler phases must be identified to You identify all the system libraries to CMS by coding the filemode
letter that corresponds to that DOS/VS system disk on the SET DOS eN
command when you invoke the CMS/DOS environment. You identify a private
library by coding ASSGN and DLBL commands that describe it. The DOS/VS system and private disks must be linked to your virtual machine and
accessed before you issue the commands to identify them for CMS. CMS/DOS has no effect on the update procedures for COBOL, or DOS PL/I. Normal update procedures
IBM-distributed coding changes apply. DOS/VS, DOS/VS for applying
For detailed information on how to generate VM/370 with CMS/DOS, refer to the publication gng §yide. VM/370 Directory Entries
The DOS/VS system and private libraries are accessed in read-only .ode
under CMS/DOS. If more than one CMS virtual machine is using the eMS/DOS environments you should update the VM/370 directory entries so
that the DOS/VS system residence volume and the ros/vs private libraries
are shared by all the eMS/DOS users.
The VM/370 directory entry for one of the CMS virtual machines should
contain the MDISK statements defining the DOS/VS volumes. The VM/370 directory entries for the other CMS/DOS users should contain LINK statements ..
For example, assume the DOS/VS system libraries are on cylinders 0 through 149 of a 3330 volume labeled DOSRES. And, assume the DOS/VS private libraries are on cylinders 0 through 99 of a 2314 volume labeled DOSPRI. Then, one eMS machine (for example, DOSUSER1) would have the MDISK statements in its directory entry. USER DOSUSER1 password 320K 2M G MDISK 331 3330 0 150 DOSRES R rpass MDISK 231 2314 0 100 DOSPRI R rpass
All the other CMS/DOS users would have links to these disks. For
example
LINK DOSUSER1 331 331 R rpass
LINK DOSUSER1 231 231 R rpass Part 3. Conversational Monitor System (CMS) 307