MO:DCA-P is the strategic AFP interchange data stream, and IPDS is the strategic AFP printer data stream.

alphabetic character. Any one of the letters A through Z (uppercase and lowercase). Some licensed programs include as alphabet characters the special characters #, $, and @.

alphanumeric. Pertaining to data that consist of letters, digits, and usually other characters, such as punctuation marks.

alternate COPY. A source library management feature that provides text inclusion within source modules, JCL streams or any other card-image data, in contrast to the standard source text inclusion features that various compilers provide.

alternate index. In systems with VSAM, a collection of index entries related to a given base cluster and organized by an alternate key, that is, a key other than the prime key of the associated base cluster data records; it gives an alternate directory for finding records in the data component of a base cluster.

AMS . See Access Method Services.

analysis routine. A routine that analyzes error records, provided by an error handler, to isolate failures to one or more field replaceable units (FRUs).

APA. all points addressable. The ability to address, reference, and position text, overlays, and images at any defined position or pel on the printable area of the paper. This capability depends on the ability of the hardware to address and to display each picture element.

APF. authorized program facility. The authorized program facility (APF) is a facility that an installation manager uses to protect the system. In MVS, certain system functions, such as all or part of some SVCs, are sensitive; their use must be restricted to users who are authorized. An authorized program is one that executes in supervisor state, or with APF authorization.

application. A set of programs, JCL jobstreams, and other programming elements written for or by users for their own data processing production.

application program. (1) A program that is specific to the solution of an application problem. Synonymous with application software. (2) A program written for or by a user that applies to the users work, such as a program that does inventory control or payroll. (3) In SDF/CICS, the program using the physical maps and symbolic description maps generated from a source map set.

application program interface (API). A functional interface supplied by the operating system or by a

separately orderable licensed program that allows an application program written in a high-level language to use specific data or functions of the operating system or the licensed program.

application software. (1) Software that is specific to the solution of an application problem. (2) Software coded by or for an end user that performs a service or relates to the users work. See also system software.

application step. A job step that executes a user program directly related to data processing production. Contrast with utility step.

archive. A copy of one or more files or a copy of a database that is saved for future reference or for recovery purposes in case the original data is damaged or lost.

array. In programming languages, an aggregate that consists of data objects, with identical attributes, each of which may be uniquely referenced by subscripting.

ascending sequence. The arrangement of data in order from the lowest value to the highest value, according to the rules for comparing data. Contrast with descending sequence.

assembler language. A source language that includes symbolic machine language statements in which there is a one-to-one correspondence with the instruction formats and data formats of the computer.

asynchronous processing. A series of operations performed separately from job in which they were requested; for example, submitting a batch job from an interactive job at a workstation. Contrast with synchronous processing.

audit. To review and examine the activities of a data processing system mainly to test the adequacy and effectiveness of procedures for data security and data accuracy. See computer-system audit. See also audit review file, audit trail.

authorization. (1) In computer security, the right granted to a user to communicate with or make use of a computer system. (2) The process of granting a user either complete or restricted access to an object, resource, or function.

authorized library. A library that may contain authorized programs.

authorized program. A system program or user program that is allowed to use restricted functions.

automatic restart. A restart that takes place during the current run, that is, without resubmitting the job. An automatic restart can occur within a job step or at the beginning of a job step. Contrast with deferred restart.

566VSE to OS/390 Migration Workbook

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IBM manual VSE 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.