|
BPAM
In IBM mainframe operating systems, basic partitioned access method (BPAM) is an access method for libraries, called partitioned datasets (PDSes) in IBM terminology. BPAM is used in OS/360, OS/VS2, MVS, z/OS, and others. A PDS consists of members (internally identical to sequential data sets), registered in a list called the ''directory''. The combination of members and directory is a single dataset on disk. The directory contains a list of member's names (8 characters, padded on the right with blanks, as required) and member's addresses. Addresses are relative to the start of the dataset in order to allow the PDS to be moved to a different disk location. Partitioned datasets can store any type of data, but they are often used to store executable programs, or ''load modules'', sometimes called binaries in other systems. Other uses include system assembler macro definitions, job control procedures, and program source code. Application program interface BPAM provides an appl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Access Method
An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. Access methods were present in several mainframe operating systems since the late 1950s, under a variety of names; the name ''access method'' was introduced in 1963 in the IBM OS/360 operating system.M. A. Auslander, D. C. Larkin, A. L. Scherr: "The Evolution of the MVS Operating System", pages 478-479 Access methods provide an application programming interface (API) for programmers to transfer data to or from device, and could be compared to |
Partitioned Dataset
In the context of IBM mainframe computers in the S/360 line, a data set (IBM preferred) or dataset is a computer file having a record organization. Use of this term began with, e.g., DOS/360, OS/360, and is still used by their successors, including the current z/OS. Documentation for these systems historically preferred this term rather than ''file''. A data set is typically stored on a direct access storage device (DASD) or magnetic tape, however unit record devices, such as punch card readers, card punches, line printers and page printers can provide input/output (I/O) for a data set (file). Data sets are not unstructured streams of bytes, but rather are organized in various logical record and block structures determined by the DSORG (data set organization), RECFM (record format), and other parameters. These parameters are specified at the time of the data set allocation (creation), for example with Job Control Language DD statements. Within a running program they are stored ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS/360
OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was influenced by the earlier IBSYS/IBJOB and Input/Output Control System (IOCS) packages for the IBM 7090/7094 and even more so by the PR155 Operating System for the IBM 1410/ 7010 processors. It was one of the earliestJust a few years after Atlas Supervisor, Burroughs MCP and GECOS operating systems to require the computer hardware to include at least one direct access storage device. Although OS/360 itself was discontinued, successor operating systems, including the virtual storage MVS and the 64-bit z/OS, are still run and maintain application-level compatibility with OS/360. Overview IBM announced three different levels of OS/360, generated from the same tapes and sharing most of their code. IBM eventually renamed these options and made some significant design changes: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Set (IBM Mainframe)
In the context of IBM mainframe computers in the S/360 line, a data set (IBM preferred) or dataset is a computer file having a record organization. Use of this term began with, e.g., DOS/360, OS/360, and is still used by their successors, including the current z/OS. Documentation for these systems historically preferred this term rather than ''file''. A data set is typically stored on a direct access storage device (DASD) or magnetic tape, however unit record devices, such as punch card readers, card punches, line printers and page printers can provide input/output (I/O) for a data set (file). Data sets are not unstructured streams of bytes, but rather are organized in various logical record and block structures determined by the DSORG (data set organization), RECFM (record format), and other parameters. These parameters are specified at the time of the data set allocation (creation), for example with Job Control Language DD statements. Within a running program they are stored ... [...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] |
Data Control Block
In IBM mainframe operating systems, such as OS/360, MVS, z/OS, a Data Control Block (DCB) is a description of a dataset in a program. A DCB is coded in Assembler programs using the DCB macro instruction (which expands into a large number of "define constant" instructions). High level language programmers use library routines containing DCBs. A DCB is one of the many ''control blocks'' used in these operating systems. A ''control block'' is a data area with a predefined structure, very similar to a C struct, but typically only related to system's functions. A DCB may be compared to a FILE structure in C, but it is much more complex, offering many more options for various access methods. The control block acted as the Application programming interface between Logical IOCS and the application program and usually was defined within (and resided within) the application program itself. The addresses of I/O subroutines would be resolved during a linkedit phase after compilation or else ... [...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] |
Kernel (operating System)
The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory and facilitates interactions between hardware and software components. A full kernel controls all hardware resources (e.g. I/O, memory, cryptography) via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the utilization of common resources e.g. CPU & cache usage, file systems, and network sockets. On most systems, the kernel is one of the first programs loaded on startup (after the bootloader). It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit. The critical code of the kernel is usually loaded into a separate area of memory, which is protected from access by application ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linkage Editor
In computing, a linker or link editor is a computer system program that takes one or more object files (generated by a compiler or an assembler) and combines them into a single executable file, library file, or another "object" file. A simpler version that writes its output directly to memory is called the ''loader'', though loading is typically considered a separate process. Overview Computer programs typically are composed of several parts or modules; these parts/modules do not need to be contained within a single object file, and in such cases refer to each other by means of symbols as addresses into other modules, which are mapped into memory addresses when linked for execution. While the process of linking is meant to ultimately combine these independent parts, there are many good reasons to develop those separately at the source-level. Among these reasons are the ease of organizing several smaller pieces over a monolithic whole and the ability to better define the pur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asynchronous I/O
In computer science, asynchronous I/O (also non-sequential I/O) is a form of input/output processing that permits other processing to continue before the transmission has finished. A name used for asynchronous I/O in the Windows API is overlapped I/O. Input and output (I/O) operations on a computer can be extremely slow compared to the processing of data. An I/O device can incorporate mechanical devices that must physically move, such as a hard drive seeking a track to read or write; this is often orders of magnitude slower than the switching of electric current. For example, during a disk operation that takes ten milliseconds to perform, a processor that is clocked at one gigahertz could have performed ten million instruction-processing cycles. A simple approach to I/O would be to start the access and then wait for it to complete. But such an approach (called synchronous I/O, or blocking I/O) would block the progress of a program while the communication is in progress, leaving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block (data Storage)
In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a maximum length; a ''block size''. Data thus structured are said to be ''blocked''. The process of putting data into blocks is called ''blocking'', while ''deblocking'' is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. For some devices, such as magnetic tape and CKD disk devices, blocking reduces the amount of external storage required for the data. Blocking is almost universally employed when storing data to 9-track magnetic tape, NAND flash memory, and rotating media such as floppy disks, hard disks, and optical discs. Most file systems are based on a block device, which is a level of abstraction for the hardwar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
