DOS/VS Support Under eMS eMS supports interactive program development for DOS/VS Release 31, 32,
33 and 34. This includes creating, compiling, testing, debugging, and
executing commercial application programs. The DOS/VS progra.s can be
executed in a eMS virtual machine or in a eMS Batch Facility virtual
.achine. DOS/VS files and libraries can be read under data sets can be read and written under The CMS DOS environment (called CMS/DOS) provides many of the sa.e
facilities that are available in DOS/VS. However, CMS/DOS supports only
those facilities that are supported by a single (background) partition.
The DOS/VS facilities supported by CMS/DOS are: • DOS/VS linkage editor support • DOS/VS Supervisor and I/O macros • DOS/VS Supervisor control block support • Transient area support • DOS/VS VSAM macros
This environment is entered each time the CMS SET DOS ON command is
issued; VSAM functions are available in CMS/DOS only if the SET DOS ON (VSAM) command is issued. In the CMS/DOS environment, CMS supports many tOS/VS facilities, but does not support as simulation. When you no
longer need DOS/VS support under CMS, you issue the SET DOS OFF command and DOS/VS facilities are no longer available. CMS/DOS can execute programs that use the sequential (SAM) and virtual storage access method (VSAM), and can
libraries.
access method
access DOS/VS CMS/DOS cannot execute programs that have execution-time
restrictions, such as programs that use sort exits, teleprocessing
access methods, or multitasking. DOS/VS COBOL, DOS PL/I, and Assembler
language programs are executable under CMS/DOS. All of the CP and CMS online debugging and testing facilities (such
as the CP ADSTOP and STORE commands and the CMS DEBUG environment) are
supported in the CMS/DOS environment. Also, CP disk error recording and
recovery is supported in CMS/DOS. With its support of a CMS/DOS environment, CMS becomes an important
tool for DOS/VS application program development. Because CMS/DOS was
designed as a DOS/VS program development tool, it assumes that a DOS/VS system exists, and uses it. The following sections describe what is
supported, and what is not. CMS SUPPORT FOR OS AND DOS VSAM FUNCTIONS CMS supports interactive program development for
using VSAM. CMS supports VSAM for as programs
as/vs COBOL, or OS PL/I programming languages; or
in DOS/VS COBOL or DOS PL/I programming languages. VSAM for OS or DOS assembler language programs. OS and DOS programs written in VS BASIC, DOS programs written CMS does not support
2-48 IBM VM/370 System Logic and program Determination--VoluMe 2

eMS also supports Access Method Services to manipulate as and DOS VSAM and SAM data sets. Under eMS, VSAM data sets can span up to nine DASD volumes. CftS does
not support VSAM data set sharing; however, eftS already supports the
sharing of minidisks or full pack minidisks. VSAM data sets created in eMS are not in the eMS file format.
Therefore, CMS commands currently used to manipulate CftS files cannot be
used for VSAM data sets which are read or written in CftS. A VSAft data
set created in CMS has a file format that is compatible with as and DOS VSAM data sets. Thus a VSAM data set created in CMS can later be read
or updated by as or DOS. Because VSAM data sets in CMS are not a part of the CMS file system, eMS file size, record length, and minidisk size restrictions do not
apply. The VSAft data sets are manipulated with Access ftethod Services programs executed under instead of with the CMS file system commands. Also, all VSAM minidisks and full packs used in CMS must be
initialized with the IBCDASDI program; the CMS FORMAT co •• and must not
be used. CMS supports VSAM control blocks with the GENCB, MODCB, TESTCB, and SHOWCB macros.
In its support of VSAM data sets, CMS uses BPS (rotational position
sensing) wherever possible. eMS does not use RPS for 2314/2319 devices,
or for 3340 devices that do not have the feature.
Because CMS support of VSAM data sets is based on DOS/VS VSAM and DOS/VS Access Method Services, only disks supported by DOS/VS can be used for VSAM data sets in eMS. These disks are: • IBM 2314 Direct Access Storage Facility • IBM 2319 Disk Storage • IBM 3330 Disk Storage, Models 1 and 2 • IBM 3330 Disk Storage, Model 11 • IBM 3340 Direct Access storage Facility • IBM 3344 Direct Access Storage • IBM 3350 Direct Access Storage CMS Introduction 2-49