Figures

1.VAE with Three Address Spaces . . . . . . . . . . . . . . . . . . . . . . . . 6

2. VAE with Four Address Spaces . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.VSE/ESA Storage Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.OS/390 Storage Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.Migration Team . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

6.

Progressive versus Mass Conversion

. . . . . . . . . . . . . . . . . . . . .

49

7.

Nonstandard Labels Supported by VSE

. . . . . . . . . . . . . . . . . . .

107

8.Extract from WSC Flash 9741 . . . . . . . . . . . . . . . . . . . . . . . . . 113

9. OS/390 Master and User Catalog Structure . . . . . . . . . . . . . . . . 116

10.OS/390 VSAM Integrity Provided by Cross-Region Shareoptions . . . . 126

11.Example of an MVS CICS/OS System using MRO . . . . . . . . . . . . . 136

12.CICS Domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

13. Log Stream Choices Resulting from Hardware and Software Used . . 146

14.MVS Data Sets used by CICS . . . . . . . . . . . . . . . . . . . . . . . . . 146

15.

DL/I Functions Requiring Attention when Migrating to IMS/VS

169

16.

Steps in Migrating DL/I Databases to IMS/ESA

177

17.VTAM Start Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

18.Comparison of IBM COBOLs . . . . . . . . . . . . . . . . . . . . . . . . . 250

19.Compiler Options Comparison DOS/VS COBOL and COBOL for OS/390

and VM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

20.Recommended COBOL for OS/390 and VM Compiler Options for

Converted VS COBOL II Programs . . . . . . . . . . . . . . . . . . . . . . 262

21.Compiler Options Comparison VS COBOL II and COBOL for OS/390

and VM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

22.Reserved Words in COBOL for OS/390 and VM and not in DOS/VS

COBOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

23.Reserved Words in COBOL for OS/390 and VM for Unsupported

Features

. . . . . . . . .

264

24. Compiler Directing Words in COBOL for OS/390 and VM

. . . . . . . .

264

25.Reserved Words in COBOL for OS/390 and VM and not in VS COBOL II 265

26.Reserved Words in COBOL for OS/390 and VM for Object-Oriented

COBOL Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

27.VSE Subroutine Linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

28.MVS Subroutine Linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

29.

Sample Initiation Termination Coding . . .

. . . . . . . . . . . . . . . . .

274

30.

VSE and MVS Time Degrees of Precision

. . . . . . . . . . . . . . . . .

279

31.

Comparison of the DTFCD and DCB Macros

. . . . . . . . . . . . . . . .

295

32.Card File Macros in VSE and MVS . . . . . . . . . . . . . . . . . . . . . . 295

33.

Card File Programs in VSE and MVS

296

34.

Comparison of the DTFPR and DCB Macros

297

35.

Comparison of the DTFMT and DCB Macros

302

36.

Tape File Programs in VSE and MVS

303

37.

Comparison of DTFDI and DCB macros

304

38.

Comparison of the DTFSD and DCB Macros

310

39.

Sequential DASD FILE Program in VSE and MVS

311

40.

Comparison of DTFDA and DCB Macros

312

41.

VSE Error Bytes and MVS Exception Code Bits

313

42.

Record Reference by ID in VSE and MVS

317

43.

Record Reference by KEY in VSE and MVS

318

44.Updating a DAM File under MVS . . . . . . . . . . . . . . . . . . . . . . . 318

45.Adding to a DAM File under MVS . . . . . . . . . . . . . . . . . . . . . . 319

© Copyright IBM Corp. 1998

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IBM OS/390 manual Figures, Xvii

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.