z/OS与OS/390 UNIX上C++应用开发指南

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"CC++ Applications on zOS and OS390 UNIX"是一份由IBM红皮书提供的技术文档，专注于在IBM大型机系统z/OS（原名OS/390）和其基于UNIX的环境上开发和移植C/C++应用程序。该文档的作者包括Michael MacIsaac、Ralph Best、Johan Koppernaes、Ka Yin Lam、Raymond Mak、Daniel Prevost和George Reid等专家，他们共同探讨了如何编写可移植的C/C++代码，并在实际场景中描述了这种移植过程。本书的第二版发布于2001年12月，适用于z/OS的第1版第2个修订版本以及更早的OS/390程序版本5647-A01。这份资料具有版权，所有权利归IBM公司所有，非美国政府用户在使用时需要遵守GSA ADP Schedule合同中关于限制复制和分发的规定。文档的主要内容涵盖了以下几个关键知识点： 1. 平台兼容性：作者强调了编写能够在z/OS和OS390 UNIX环境下运行的C/C++代码的重要性，这意味着开发者需要确保他们的代码能够在不同的操作系统架构上实现无缝迁移。 2. 移植策略：书中详细阐述了如何通过编写平台无关的代码和利用标准库来实现应用的跨平台支持，以减少在从UNIX迁移到z/OS时可能遇到的问题。 3. 实战案例：文档提供了实际工作中遇到的案例研究，展示了如何处理特定问题，如内存管理、文件系统接口、网络编程等方面，以帮助读者更好地理解和应用这些技术。 4. 国际技术支持：提及了IBM的国际技术支持组织，表明IBM提供了丰富的资源和技术支持，以协助开发者解决在移植过程中可能遇到的技术难题。 5. 用户指南和反馈：文档鼓励读者向IBM提供反馈，表明了IBM对于持续改进和适应用户需求的态度，同时也确保了文档的更新性和实用性。 6. 版权和许可：最后，文档明确了使用权限，指出当用户发送信息至IBM时，他们同意IBM可以自由使用或以适合的方式分发这些信息，而无需对用户承担任何义务。 "CC++ Applications on zOS and OS390 UNIX"是一份实用的指南，为IT专业人士提供了解决大型机系统上C/C++应用开发和移植问题的重要参考资料，旨在促进软件开发的高效性和兼容性。

xiv C/C++ Applications on z/OS and OS/390 UNIX

Chapter 1. z/OS and OS/390 tools

z/OS, formerly named OS/390, is the flagship operating system that runs on IBM’s S/390

enterprise servers (after OS/390 V2R10 in September of 2000, z/OS V1R1 was released in

March of 2001). S/390 servers store and support programs that process much of the data

used by the world’s largest corporations. The strength of z/OS lies in its ability to concurrently

and reliably support thousands of users using many diverse applications.

Herein lies the major difference between the z/OS environment and most UNIX environments.

UNIX environments usually support a single server, application, or related set of users. So if

UNIX is supporting all three types of applications, three UNIX servers are used.

z/OS, on the other hand, rarely supports a single application or set of users. Rather, it might

be supporting a mix of open and traditional z/OS applications. A single z/OS operating

system image (copy of z/OS) could be supporting Web browsers, e-mail, transaction

managers, database managers, TSO, and batch users.

z/OS provides an extensive set of tools and facilities to enable an installation to gain the

maximum benefit from this rich and diverse environment. It provides a WorkLoad Manager

(WLM) to allow classes of applications to be prioritized so that each user and application gets

its fair share of z/OS resources. It allows a wide variety of System Management Facilities

(SMF) records to be created for resource accounting, performance analysis, and auditing

purposes.

z/OS also supports multiple layers of recovery routines and a Parallel Sysplex environment to

provide essentially continuous availability. It provides a full set of Resource Measurement

Facility (RMF) monitors and reports for analyzing the performance or capacity of a z/OS

system.

z/OS provides a number of interfaces that users can use in requesting z/OS services. This

rich and comprehensive set of interfaces and tools provides z/OS with the flexibility and

versatility to match the multitude of applications that run under z/OS. This chapter provides a

brief look at some of the most important tools, facilities, and applications in the z/OS

environment. But first we discuss ways of accessing services on the z/OS system.

2 C/C++ Applications on z/OS and OS/390 UNIX

1.1 User access under z/OS

z/OS provides several classes of traditional operating system interfaces, but the two most

important are

batch and TSO:

򐂰 Batch is the main vehicle for invoking programs (binary executables) in z/OS.

򐂰 TSO provides an interactive command line interface to z/OS operating system services.

TSO in z/OS plays a role similar to the shell in UNIX. However, very few installations still use

TSO. Most use its enhanced add-on called Time Sharing Option/Extended (TSO/E).

Therefore, we will look at TSO/E, but let us first examine batch and the Job Control Language

(JCL) environment.

1.1.1 JCL and batch

z/OS runs work in the background via batch job submission. The three most important JCL

statements are:

򐂰 JOB statement

򐂰 EXEC statement

򐂰 DD statement

Any interesting job stream (job) in z/OS contains all three types of statements. Only the DD

statement is optional, but you will probably never see a job without one. There are several

types of datasets (

dataset is the z/OS equivalent of a UNIX file), and numerous dataset

characteristics in z/OS. Thus it is the DD statement that allows the large number of parameter

and subparameter coding combinations. It is the most difficult statement to learn to code. We

briefly describe all three types of statements.

1.1.2 JOB statement

The Job statement marks the beginning of the job. It identifies the user, specifies accounting

information, and sets limits on the z/OS resources that can be consumed by the job.

1.1.3 EXEC statement

The EXEC statement identifies a job step and a program (or JCL procedure) that is to be

invoked in that step. It also provides processing information for that step.

1.1.4 DD statement

The DD statement describes a dataset that will presumably be used by the program referred

to on the EXEC statement. The DD statement identifies input and/or output resources for the

dataset.

A sample job

Here is a sample job containing one statement of each type:

//RALPHBA JOB (999,POK),'BEST, R',MSGLEVEL=(1,1),REGION=6M,

// CLASS=A,MSGCLASS=H,TIME=1

//ACT EXEC PGM=IEFBR14

//SOUT DD DSN=RALPHB.STD.OUT,SPACE=(TRK,(1,1)),UNIT=SYSDA,DISP=(,CATLG)

This job will cause z/OS to execute a program, IEFBR14. z/OS will also create and catalog a

disk dataset, RALPHB.STD.OUT. Syntax information and more detail about these statements

can be found in the publication OS/390 MVS JCL Reference, GC28-1757.

JCL is either directly or indirectly involved almost every technique that is used to invoke

executable programs in z/OS. Batch is just one of several vehicles that exploit JCL. But it is

the JCL and not the batch that is really important. It takes time to gain a comprehensive,

proficient working knowledge of JCL, but it is not usually necessary to learn a lot of JCL to

work in the z/OS environment.

A number of enhancements and components have been introduced over the years to

minimize the amount of JCL you need to learn to be proficient. Some of these enhancements

and components are JCL procedures, Storage Management Subsystem (SMS), and even the

Interactive System Productivity Facility/Product Development Facility (ISPF/PDF). But JCL is

still fundamental to the environment. Most JCL is created today through ISPF/PDF. The

interface that supports ISPF/PDF is TSO/E.

1.1.5 TSO/E

TSO/E provides a z/OS interactive, command-line interface similar to the shell in the UNIX

environment. Of course, this similarity cannot be taken too far. A sample TSO/E command is:

ALLOCATE DA('RALPHB.STD.OUT') OLD

This command will allocate the existing z/OS disk dataset, RALPHB.STD.OUT. However, this

dataset could also have been created through TSO/E dynamic allocation by using the same

ALLOCATE command. Syntax information and more detail about these commands can be

found in OS/390 TSO/E Command Reference, SC28-1969.

We compared TSO/E to the shell and mentioned that both use a command line interface.

Many people think the command line interface is difficult to work with. This was evidenced by

the acceptance of Windows over the older DOS operating system. The distaste for the

command line interface also gave rise to the X Window system in UNIX.

In z/OS, TSO/E has given way to ISPF/PDF, which uses panel-driven dialogs, action bars,

and pull-down menus. It lets users make alphanumeric requests from various panels, and

provides action bars and pull-down menus as an alternative to the panel dialog interface.

1.1.6 ISPF/PDF

This is a widely used interface that almost everyone uses with TSO/E. ISPF/PDF takes a little

time to enunciate, so many people refer to it simply as ISPF.

We mentioned that ISPF/PDF is used to build JCL job streams and submit the jobs. It also

supports the System Display and Search Facility (SDSF), which is used to monitor job

execution and then review the jobs after termination.

But ISPF/PDF is used for much more. It provides a user-friendly full screen editor. It allows

users to invoke a number of z/OS utilities or issue TSO/E commands. It also provides an

environment that facilitates the development and management of interactive applications.

A wide range of other TSO/E-based interactive applications are supported and invoked

through ISPF/PDF. For example, a few of the other interactive applications that can be

invoked from under this ISPF/PDF umbrella are the OMVS UNIX shell, the ISHELL, RACF

panels for securing the z/OS traditional and open environments, WLM interfaces for

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