sequential data set. A data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape. Contrast with direct data set.

sequential file. A file in which records are processed in the order in which they are entered and stored in the file. Contrast with direct file, indexed file.

sequential processing. (1) The processing of logical records in the order in which they are accessed. (2) The processing of records in the order in which they exist in a file. Synonymous with consecutive processing.

ServerPac. A software delivery package consisting of installed products and integrated service for a

ready-to-IPL system. To install, you use the CustomPac Installation Dialog -- the same dialog that is used for all the CustomPac offerings, including SystemPac and ProductPac.

shared spooling. A function that permits the VSE/POWER account file, data file, and queue file to be shared among several computer systems with VSE/POWER.

SIE. SoftwareXcel Installation Express. A service offering in the USA built on SystemPac with IBM assistance included for installation and implementation.

simulation. (1) The use of a data processing system to represent selected behavioral characteristics of a physical or abstract system; for example, the representation of air streams around airfoils at various velocities, temperatures, and air pressures.

(2) Contrast with emulation.

sliding window. A technique to determine the

century (high-order digits) of a year when represented by two digits. The user specifies the number of years (both past and future) within a 100-year window spanning two centuries. For example, assume the window is set at 19 future years (1996-2014) and 80 past years (1915-1994). Dates in the range 00-14(inclusive) are designated 21st century dates because they fall into the future window. Dates in the range 15-99(inclusive) fall into the 20th century.

SMF. system management facilities. A component of MVS and OS/390 that collects input/output (I/O) statistics, provided at the data set and storage class levels, which helps you monitor the performance of the direct access storage subsystem.

SMP/E. System Modification Program Extended. SMP/E is the IBM product designed to install new function and subsequent service into target libraries and distribution libraries.

SMS . Storage Management Subsystem. A DFSMS/MVS or MVS/DFP facility used to automate and centralize the management of storage.

SNA network. The part of a user-application network that conforms to the formats and protocols of Systems Network Architecture. It enables reliable transfer of data among end users and provides protocols for controlling the resources of various network configurations. The SNA network consists of network accessible units (NAUs), boundary function, gateway function, and intermediate session routing function components; and the transport network.

software. All or part of the programs, procedures, rules, and associated documentation of a data processing system. Software is an intellectual creation that is independent of the medium on which it is recorded.

source code. The input to a compiler or assembler, written in a source language. Contrast with object code.

source language. The programming language for expressing source programs that a particular translator can accept.

source program. (1) A set of instructions written in a programming language that must be translated to machine language before the program can be run. (2) Contrast with object program.

source statement. A statement written in symbols of a programming language; for example, RPG, COBOL, BASIC, and PL/I specifications are source statements.

spool file. (1) A file that contains output data that has been saved for later processing. (2) One of three VSE/POWER files on disk: queue file, data file, and account file.

spreadsheet. A worksheet arranged in rows and columns, in which a change in the contents of one cell can cause electronic recomputation of one or more cells, based on user defined relations among the cells.

stand-alone. Pertaining to operation that is independent of any other device, program, or system.

standard label. A fixed-format record that identifies a volume of data such as a tape reel or a file that is part of a volume of data.

statement. In programming languages, a language construct that represents a step in a sequence of actions or a set of declarations.

storage location. A position in a storage device that is uniquely specified by means of an address.

G l o s s a r y 579

Page 603
Image 603
IBM OS/390 manual O s s a r y

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.