A DOS/VS private library is usable when it is: • Defined for your virtual illachine • Accessed • Identified via ASSGN and DLBL commands
Performance
Although you can use the CMS/DOS library services to place the DOS/VS COBOL compiler, DOS PL/I compiler, and ESERV program in a CMS DOSLIB, it
is recommended that you do not use this method with VM/370. CMS/DOS can
fetch these directly from the DOS/VS system or private libraries faster
than from a DOSLIB. Execution Considerations and Restrictions
The eMS/DOS environment does not support the execution of DOS programs
that use: • Sort exits. The DOS/VS COBOL and DOS PL/I SORT verbs are net
supported in CMS/DOS. • Teleprocessing or indexed sequential (ISAH) access methods. eMS/DOS supports only the sequential (SAM) and virtual storage (VSAM) access
methods. • Multitasking. CMS/DOS background partition.
supports only a single partition, the CMS/DOS can be executed in a CMS Batch Facility virtual machine. If
any of the DOS programs that are executed in the batch machine read data
from the card reader, you must ensure that the end-of-data indication is
recognized. Be sure that (1) the program checks for end of data and (2)
a /* record follows the last data record.
If there is an error in the way you handle end of data, the Des
program could read the entire batch input stream as its own data. The
result is that jobs sent to the batch machine are never executed and the DOS program reads records that are not part of its input file.
Part 3. Conversational Monitor System (CMS) 309

eMS Support for OS and DOS VSAM Functions CMS supports interactive program development for
using VSAM. CMS supports VSAM for as proqrams OS/VS COBOL, or as PL/I programming languages; or
in DOS/VS COBOL or DOS PL/I programming languages. VSAM for as or DOS Assembler language programs.
as and DOS programs
written in VS BASIC, DOS programs CMS does not support CMS also supports Access Method Services to manipulate as and Des VSAM and SAM data sets. Under CMS, VSAM data sets can span up to nine DASD volumes. CMS does
not support VSAM data set sharing; however, CMS already supports the
sharing of minidisks or full pack minidisks. VSAM data sets created in CMS are not in the CMS file format.
Therefore, CMS commands currently used to manipulate CMS files cannot be
used for VSAM data sets that are read or written in CMS. A VSAM data
set created in CMS has a file format that is compatible with as and Des 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 eMS are not a part of the CMS file system, CMS file size, record length, and minidisk size restrictions do not The VSAM data sets are manipulated with Access Method Services programs executed under CMS, 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 command 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. CMS does not use RPS for 2314/2319 devices,
or for 3340 devices that do not have the feature.
Hardware Devices Supported
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 fer VSAM data sets in CMS or for CMS disk files used as input for Access Method Services. 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 310 IBM VM/370 System Programmer's Guide