V

verification test. A test of a system to prove that it meets all its specified requirements at a particular stage of its development.

virtual address. The address of a location in virtual storage. A virtual address must be translated into a real address in order to process the data in processor storage.

virtual address space. (1) In virtual storage systems, the virtual storage assigned to a batched or terminal job, a system task, or a task initiated by a command.

(2)In VSE, a subdivision of the virtual address area available to the user for the allocation of private, nonshared partitions.

virtual device. A device that appears to the user as a separate entity, but is actually a shared portion of a real device; for example, several virtual terminals can exist simultaneously, but only one is active at any given time.

virtual disk. (1) Main storage used as if it were a disk device. (2) In VM, a physical disk storage device, or a logical subdivision of a physical disk storage device, that has its own address, consecutive storage space for data, and index or description of stored data so that the data can be accessed.

virtual machine (VM). A virtual data processing system that appears to be at the exclusive disposal of a particular user, but whose functions are accomplished by sharing the resources of a real data processing system.

virtual storage. The storage space that may be regarded as addressable main storage by the user of a computer system in which virtual addresses are mapped into real addresses. The size of virtual storage is limited by the addressing scheme of the computer system and by the amount of auxiliary storage available, not by the actual number of main storage locations.

Virtual Storage Access Method (VSAM). An access method for indexed or sequential processing of fixed and variable-length records on direct access devices.

volume label. An area on a standard label tape used to identify the tape volume and its owner. This area is the first 80 bytes and contains VOL 1 in the first four positions.

volume serial number. A number in a volume label assigned when a volume is prepared for use in a system.

VSAM managed space. A user-defined space on disk that is under the control of VSAM.

VSE (Virtual Storage Extended). Any of the VSE operating systems and environments.

W

warm start. (1) A restart that allows reuse of previously initialized input and output work queues.

(2)In VM, the result of an initial program load (IPL) that does not erase previous system data.

work file. (1) A file used for temporary storage of data being processed. (2) In sorting, an intermediate file used for temporary storage of data between phases.

work space. That portion of main storage that is used by a computer program for temporary storage of data. Synonymous with working space.

write access. In computer security, permission to write to an object.

Y

Year2000 challenge. The potential problems and its variations that might be encountered in any level of computer hardware or software from microcode to application programs, files, and databases that need to correctly interpret year-date data represented in 2-digit-year format caused by the transition to the year 2000.

Year2000 ready. The capability of a Product, when used in accordance with its associated documentation, to correctly process, provide and/or receive date data within and between the 20th and 21st centuries, provided that all products (for example, hardware, software, and firmware) used with the Product properly exchange accurate date data with it.

Year2000 support. The ability to provide Year2000 readiness.

Year2000 transition. The process of revising systems and databases) to correctly process date data both within and between the 20th and 21st centuries.

YY format. Synonymous with 2-digit-year format.

YYYYformat. Synonymous with 4-digit-year format and a subset of CCYY format.

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IBM OS/390 manual Year2000 support. The ability to provide Year2000 readiness

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.