comparing (continued) PSF commands 242 VSE & MVS JCL 86, 91

compatibility 344, 346

compiler option considerations for VS COBOL II 261 compiler options 260, 335

compiler options unavailable with COBOL for OS/390 and VM 260

compiling converted COBOL programs 265 complexity of implementation 51 component terminology for MVS 21 COMPRESS 121

Computer Associates 525 COMREG (DATE and UPSI) 81 COMRG 277

conceptual differences between LE/VSE & OS/390 Language Environment 352

COND parameter 85 conditional JCL 73, 84 conditional JCL - MVS 84 configuration management 469

methodology 470 overview 469 tasks 469

CONFIGURATION SECTION - SPECIAL-NAMES paragraph 255

configuring hardware 402 connectivity 11

considerations for DASD sharing 130 console control 444

console modes 444

console operator interface 25 continuation cards 72 control commands 233 control statements 377, 379 controlling

batch jobs 451 consoles 444 devices 448

displaying the status of devices 448 JES2 commands 450

JES2 devices 449 jobs 449

MVS commands 450 OS/390 system 447

RMF and other monitors 450 SDSF device panels 449 SDSF panels 450

started tasks 449, 451 starting the system 447 stopping JES2 448 time sharing users 451 TSO users 449

understanding device allocation 448 conversion

actual 516

all VSE COBOL compilers 259 Assembler comments 267

conversion (continued) CA-Convertor 525

CICS Command Level Conversion Aid 522 compiling converted COBOL programs 265 DISPLAY statement 259

dummy 52 final JCL 516 final program 517

FORTRAN considerations 349 from COBOL for VSE/ESA 259 from DOS/VS COBOL 252 from VS COBOL II 258

ICCF libraries 163 method 42 phases 503

pilot 52

PL/I programs 345

running converted COBOL programs 265 services and tools 519

specifications 499 trial 505

VSAM 259

VSE COBOL compilers 259

VSE/ESA facilities 520

VSE/VSAM catalog 118

conversion considerations for all VSE COBOL compilers 259

conversion phases initialization testing 511 JCL conversion 504 parallel/production simulation testing

data migration 514

date concerns during parallel testing 515 job simulation 515

Phase 4: initial trial conversion 505

Phase 5: OS/390 regression tests & repeated trial conversions

DASD requirements 508 MVS tools testing 508

OS/390 automated operations tools 510 personnel involvement in testing 507 recommendations 507 responsibilities 507

Subsystem Storage Protect 508 test plan 508

testing priorities 507 program conversion

considerations 503

VSE coding practices causing conversion problems 504

system testing batch 513

data migration 514 online 513

testing converted applications 506 unit testing

batch 512

data migration 512 online 512

596VSE to OS/390 Migration Workbook

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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.
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