LINK DOSUSER1 331 331 R rpass
LINK DOSUSER1 231 231 R rpass
When the VSE System Must Be Online
Performance
Most of what you do in the CMS/DOS environment for VSE program develop­
ment requires that the VSE system pack and/or the VSE private libraries be avail­
able to CMS/DOS. In general, you need these VSE volumes whenever: You use the DOS/VS COBOL compiler or DOS/PLI Optimizing compiler.
The compilers are executed from the system or private core image libraries. Your source programs contain COPY, LIBRARY, %INCLUDE, or CBL
statements. These statements copy books from your system or the private
source statement library. You invoke one of the library programs: DSERV, RSERV, SSERV, PSERV,
or ESERV. You execute VSE programs that use LIOCS modules. CMS/DOS fetches most
of the LIOCS routines for non-disk files directly from VSE system or private
libraries.
A VSE system pack is usable when it is:
Defined for your virtual machine
Accessed
Specified, by mode letter, on the SET DOS ON command.
A VSE private library is usable when it is:
Defined for your virtual machine
Accessed
Identified via ASSGN and DLBL commands.
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 800-byte format CMS
disks. CMS/DOS can fetch these directly from the VSE system or private libraries
faster than from a DOSLIB on 800-byte format CMS disks. Fetch time from DOSLIBs on 512, 1K-, 2K-, or 4K-byte format CMS disks is approximately equiv­
alent to that of VSE system or private libraries.
Execution Considerations and Restrictions
The CMS/DOS environment does not support the execution of VSE programs that
use: • Teleprocessing or indexed sequential (ISAM) access methods. CMS/DOS supports only the sequential (SAM) and virtual storage (VSAM) access meth­
ods.
Multitasking. CMS/DOS supports only a single partition, the background par­
tition. VSE Support Under eMS 413

CMS/DOS can be executed in a CMS Batch Facility virtual machine. If any of the VSE 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 VSE 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 VSE program reads records that are not
part of its input file.
414 VM/SP System Programmer's Guide