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Service Request Block
{{unreferenced, date=December 2019 A Service Request Block (SRB) is a data structure of MVS/370 and successor versions of IBM mainframe operating systems employed mainly, but not exclusively, by the Start Input/Output interface. An SRB may be considered, in the abstract, to be a highly optimized Task Control Block (TCB), one which has few, if any, associated resources other than access to the processor itself. All system resources which are utilized under an SRB must be accessed through the use of "branch entries", some of which are new entries to traditional system services which were formerly accessed exclusively using SVC instructions (which an SRB may not employ for any purpose other than abnormally terminating itself in which case SVC 13, ABEND, may be used, however the "branch entry" to ABTERM is really more appropriate). When employed by the Start Input/Output interface, an SRB is always paired with an Input/Output Supervisor Block (IOSB). When otherwise employed, an SRB ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Structure
In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data, i.e., it is an algebraic structure about data. Usage Data structures serve as the basis for abstract data types (ADT). The ADT defines the logical form of the data type. The data structure implements the physical form of the data type. Different types of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks. For example, relational databases commonly use B-tree indexes for data retrieval, while compiler implementations usually use hash tables to look up identifiers. Data structures provide a means to manage large amounts of data efficiently for uses such as large databases and internet indexing services. Usually, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MVS/370
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unrelated to IBM's other mainframe operating system lines, e.g., VSE, VM, TPF. Overview First released in 1974, MVS was extended by program products with new names multiple times: * first to MVS/SE (MVS/System Extensions),some print media used the singular, MVS/System Extension: Computerworld, 15 Dec 1980 - Page 5; 26 June 1978 - Page 8 * next to MVS/SP (MVS/System Product) Version 1, * next to MVS/XA (MVS/eXtended Architecture), * next to MVS/ESA (MVS/Enterprise Systems Architecture), * then to OS/390 and * finally to z/OS (when 64-bit support was added with the zSeries models). IBM added UNIX support (originally called OpenEdition MVS) in MVS/SP V4.3 and has obtained POSIX and UNIX™ certifications at several different levels from IEEE, X ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM Mainframe
IBM mainframes are large computer systems produced by IBM since 1952. During the 1960s and 1970s, IBM dominated the large computer market. Current mainframe computers in IBM's line of business computers are developments of the basic design of the IBM System/360. First and second generation From 1952 into the late 1960s, IBM manufactured and marketed several large computer models, known as the IBM 700/7000 series. The first-generation 700s were based on vacuum tubes, while the later, second-generation 7000s used transistors. These machines established IBM's dominance in electronic data processing ("EDP"). IBM had two model categories: one (701, 704, 709, 7030, 7090, 7094, 7040, 7044) for engineering and scientific use, and one (702, 705, 705-II, 705-III, 7080, 7070, 7072, 7074, 7010) for commercial or data processing use. The two categories, scientific and commercial, generally used common peripherals but had completely different instruction sets, and there were incompatibiliti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 74.99%. macOS by Apple Inc. is in second place (14.84%), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Start Input/Output
In MVS/370 and successor versions of IBM mainframe operating systems, Start Input/Output (STARTIO) is a macro instruction and a "branch entry" for low-level device access, where the programmer is responsible for providing a list of device-specific CCWs, that is, a channel program, to be executed by I/O channels, control units and devices and a number of "exits", several of which may be immediate returns to the Input/Output Supervisor (IOS). Invokers of STARTIO must be in supervisor mode and key 0. STARTIO interfaces directly with the IOS component of MVS. Differences from Execute Channel Program (EXCP) Start Input/Output differs from EXCP (including XDAP, which is simply a DASD-only subset of EXCP) and EXCPVR in the following fundamental way: Start Input/Output is a low level facility that supports, e.g., selection of channel paths, selection of exposures while Execute Channel Program is a high level facility that supports, e.g., CCW translation, page fixing, serialization of r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Task Control Block
The Task Control Block (TCB) contains the state of a task in, e.g., OS/360 and successors on IBM System/360 architecture and successors. The TCB in OS/360 and successors In OS/360, OS/VS1, SVS, MVS/370, MVS/XA, MVS/ESA, OS/390 and z/OS, the TCB contains, among other data, non-dispatchability flags and the general and floating point registers for a task that is not currently assigned to a CPU. A TCB provides an anchor for a linked list of other, related request blocks (RBs); the top-linked RB for a TCB contains the Program status word (PSW) when the task is not assigned to a CPU. When the control program's dispatcher selects a TCB to be dispatched, the dispatcher loads registers from the TCB and loads the PSW from the top RB of the TCB, thereby dispatching the unit of work. Request Blocks OS/360 has the following types of request blockss ; Interruption Request Block : An IRB is used to handle an asynchronous exit. ; Program Request Block : A PRB represents a module invoked wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supervisor Call Instruction
A supervisor, or lead, (also known as foreman, boss, overseer, facilitator, monitor, area coordinator, line-manager or sometimes gaffer) is the job title of a lower-level management position that is primarily based on authority over workers or a workplace. A supervisor can also be one of the most senior in the staff at the place of work, such as a professor who oversees a PhD dissertation. Supervision, on the other hand, can be performed by people without this formal title, for example by parents. The term supervisor itself can be used to refer to any personnel who have this task as part of their job description. An employee is a supervisor if they have the power and authority to do the following actions (according to the Ontario Ministry of Labour): # Give instructions and/or orders to subordinates. # Be held responsible for the work and actions of other employees. If an employee cannot do the above, legally, they are probably not a supervisor, but in some other category, su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Input/Output Supervisor Block
An Input/Output Supervisor Block (IOSB) is a data structure employed exclusively by the Start Input/Output interface of MVS/370 and successor IBM mainframe operating systems. The IOSB describes the I/O request and passes parameters to and receives responses from the Input/Output Supervisor (IOS). An IOSB is always paired with a Service Request Block (SRB). The SRB schedules processor Processor may refer to: Computing Hardware * Processor (computing) **Central processing unit (CPU), the hardware within a computer that executes a program *** Microprocessor, a central processing unit contained on a single integrated circuit (I ... activity, as required, on any available processor in connection with the I/O request, although the I/O operation itself may have been initiated on another processor. This distinction allowed, for example, effective use of so-called "attached processors" (processors with no connected I/O devices), which were common in the early days of MVS/370, and in in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Address Space
In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve stored data, each datum must have an address where it can be located. The number of address spaces available depends on the underlying address structure, which is usually limited by the computer architecture being used. Often an address space in a system with virtual memory corresponds to a highest level translation table, e.g., a segment table in IBM System/370. Address spaces are created by combining enough uniquely identified qualifiers to make an address unambiguous within the address space. For a person's physical address, the ''address space'' would be a combination of locations, such as a neighborhood, town, city, or country. Some elements of a data address space may be the same, but if any element in the address is different, addres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inter-process Communication
In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categorized as clients and servers, where the client requests data and the server responds to client requests. Many applications are both clients and servers, as commonly seen in distributed computing. IPC is very important to the design process for microkernels and nanokernels, which reduce the number of functionalities provided by the kernel. Those functionalities are then obtained by communicating with servers via IPC, leading to a large increase in communication when compared to a regular monolithic kernel. IPC interfaces generally encompass variable analytic framework structures. These processes ensure compatibility between the multi-vector protocols upon which IPC models rely. An IPC mechanism is either synchronous or asynchronous. Synchr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ZIIP
In IBM System z9 and successor mainframes, the System z Integrated Information Processor (zIIP) is a special purpose processor. It was initially introduced to relieve the general mainframe central processors (CPs) of specific Db2 processing loads, but currently is used to offload other z/OS workloads as described below. The idea originated with previous special purpose processors, the zAAP, which offloads Java processing, and the IFL, which runs Linux and z/VM but not other IBM operating systems such as z/OS, DOS/VSE and TPF. A System z PU (processor unit) is "characterized" as one of these processor types, or as a CP (Central Processor), or SAP (System Assist Processor). These processors do not contain microcode or hardware features that accelerate their designated workloads. Instead, by relieving the general CP of particular workloads, they often lead to a higher workload throughput at reduced license fees. DB2 for z/OS V8 was the first application to exploit the zIIP, but no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process Control Block
A process control block (PCB) is a data structure used by computer operating systems to store all the information about a process. It is also known as a process descriptor. When a process is created (initialized or installed), the operating system creates a corresponding process control block. This specifies the process state i.e. new, ready, running, waiting or terminated. Role The role of the PCBs is central in process management: they are accessed and/or modified by most utilities, particularly those involved with scheduling and resource management. Structure In multitasking operating systems, the PCB stores data needed for correct and efficient process management. Though the details of these structures are system-dependent, common elements fall in three main categories: * Process identification * Process state * Process control Status tables exist for each relevant entity, like describing memory, I/O devices, files and processes. Memory tables, for example, contain infor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
