Entrypoint, Data Division File Description FD, Volseq

DOS/VS COBOL (continued)		enforcing installation standards	410
REPORT WRITER statements	253	entering and manipulating data	159
reserved word considerations	263	entitled methods of installing OS/390 406
DOS/VS COBOL & COBOL for OS/390 and VM		ENTRYPOINT 284
language differences		ENVIRONMENT attributes 338
Common COBOL Coding Problems 253		SIS option (Sequential Insert Strategy) 340
DATA DIVISION - FILE DESCRIPTION (FD) 256		supported but to be avoided	340
ENVIRONMENT DIVISION 255		TOTAL option 340

file handling considerations				unsupported in MVS
file attribute mismatches 258				ASSOCIATE		339
file status codes			257	CMDCHN WTRPROT FILESEC NOFEED
ISAM 258				VOLSEQ		339
PROCEDURE DIVISION - Input/Output				COLBIN	339
program termination 257				FUNCTION		339
DRDA considerations			182	MEDIUM	339
DSCB	108			NOTAPEMK NOLABEL 340
DSNAME sharing		128		OMR (Optical Mark Read) 339
DTFCD operands		294		RCE (Read Column Eliminate) 339
DTFCN	304			STACKER		339

DTFDA operands			311					UNLOAD			339
DTFDI operands			303					environment customer migration example 529
DTFMT operands			301					ENVIRONMENT DIVISION						255
DTFPH macro		328						environments			370
DTFPR operands			296					EOJ macro		281
DTFSD operands			309					equivalent JES2 - POWER parameters 225
dual production environment 28								ERET macro		306
dummy conversion 52								error & reason code compatibility								131
dump analysis		473						Error bytes		312
DUMP in PL/I Optimizer					343			error detection			76
compatibility			344					essential supplemental reading 134
options specific to DOS						343		estimated project schedule							54
options specific to MVS						344		EXAMINE command					477
output file		343						exclusives PSF/MVS					235
DUMP macro		280						EXCPAD routines				291
dumps 473								EXEC & PROCESS cards						338
duration customer migration						531		EXEC statement 72, 82
dynamic allocation macro					242			EXEC statement - COND parameter								85
dynamic loading of dependent programs 334								Execute macro forms					293
DYNBUF	336							executing ISPF applications							440
								executing programs at a terminal								161
E								execution options				337, 346
E								EXIT E35	341
E15 EXIT PROCEDURE				341				exits
early error detection				76				abnormal termination						365
editing data sets			438					Assembler user				364
education	49							CICS	147
application programming						31		comparisons			230
introduction			31					DITSECUR			385
operations		31						global	148
requirements			31					high-level language						364
system programming					31			installation			243
EGCS (VSE) to DBCS (OS Version 2)							333	JES2 installation					211
ELSE statement			84					LE user		364
emergency backup system						410		MVS	415
end user	178							NJE	221
end-of-page sensing				209, 217				RJE	220
ENDIF statement			84					VTAM	191
eNetwork Communications Server							188

600VSE to OS/390 Migration Workbook

OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.

IBM OS/390 Entrypoint, Data Division File Description FD, Associate, Volseq, Function, Medium

Models: OS/390

ENTRYPOINT 284

DATA DIVISION - FILE DESCRIPTION (FD) 256

ENVIRONMENT DIVISION 255

ASSOCIATE

CMDCHN WTRPROT FILESEC NOFEED

VOLSEQ

COLBIN

FUNCTION

MEDIUM

DSCB

NOTAPEMK NOLABEL 340

DTFCN

STACKER

UNLOAD

ENVIRONMENT DIVISION

DYNBUF

EXIT E35

E15 EXIT PROCEDURE

DITSECUR

system programming

RJE

600VSE to OS/390 Migration Workbook

OS/390 specifications