B

background partition. In VSE, a space of virtual storage in which programs are executed under control of the system. By default, the partition has a processing priority lower than any of the existing foreground partitions.

backout. See file and catalog backout.

backup copy. A copy of information or data that is kept in case the original is changed or destroyed.

base cluster. In systems with VSAM, a

key-sequenced or entry-sequenced file over which one or more alternate indexes are built. See also cluster.

base register. (1) A register that holds a base address. (2) A general-purpose register that a programmer chooses to contain a base address.

batch application. In VSE, a set of programs that normally processes data without user interaction; for example, an application to print a company payroll. Such an application uses a device, a data file, or the processor intensively for a longer time than online applications.

batch execution. Execution of programs and data that have been submitted or accumulated as batched input.

batch processing. (1) Loosely, the execution of computer programs serially. (2) Pertaining to the technique of executing a set of computer programs such that each is completed before the next program of the set is started.

BCP. Base Control Program. This refers to the

²heart² of the OS/390 operating system without the JES, RACF, VTAM and other subsystems.

bind. (1) To relate an identifier to another object in a program; for example, to relate an identifier to a value, an address or another identifier, or to associate formal parameters and actual parameters.

(2)To associate a variable with an absolute address, identifier, or virtual address, or with a symbolic address or label in a program.

binder. The DFSMS/MVS program that processes the output of language translators and compilers into an executable program (load module or program object). It replaces the linkage editor and batch loader in the MVS/ESA operating system.

bit string. A string consisting solely of bits.

blocking factor. The number of records in a block. A blocking factor is calculated by dividing the size of the block by the size of the record. Synonymous with grouping factor.

bootstrap. A sequence of instructions whose execution causes additional instructions to be loaded and executed until the complete computer program is in storage.

buffer pool. (1) An area of storage in which all buffers of a program are kept. (2) In ACF/VTAM, a group of buffers having the same size. A buffer pool is established at initialization time in the message control program; the buffers are built in extents chained together.

built-in function. (1) A function that is supplied by a language. (2) In PL/I, a predefined function, such as a commonly used arithmetic function or a function necessary to high-level language compilers; for example, a function for manipulating character strings or converting data. It is automatically called by a built-in function reference.

business partner. Any non-IBM organization, with whom IBM has a written contract defining a complementary marketing relationship, that provides end users with information-handling solutions that use or rely upon an IBM offering.

C

C language. A language used to develop software applications in compact, efficient code that can be run on different types of computers with minimal change.

cache. (1) A special-purpose buffer storage, smaller and faster than main storage, used to hold a copy of instructions and data obtained from main storage and likely to be needed next by the processor. (2) A buffer storage that contains frequently accessed instructions and data; it is used to reduce access time.

cancel. To end a task before it is completed.

catalog. A collection of all data set information, like device type and volume serial number, that MVS needs to locate a specific data set. Using the catalog simplifies developing MVS JCL that does not change from one run to the next.

catalog backout. See file and catalog backout.

cataloged procedure. A set of control statements placed in a library and retrievable by name.

category (of programming elements). A main classification of programming elements that groups elements of a single type, such as source modules, copied members, and macros.

CBPDO. Custom-Built Product Delivery Offering. A CBPDO is a tape that has been specially prepared for installing a particular product and the related service requested by the customer. A CBPDO simplifies installing a product and the service for it.

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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.